diff --git a/__test__/projects/GitHubProjectDataSource.test.ts b/__test__/projects/GitHubProjectDataSource.test.ts
index 6dcbda37..c98b3a8e 100644
--- a/__test__/projects/GitHubProjectDataSource.test.ts
+++ b/__test__/projects/GitHubProjectDataSource.test.ts
@@ -87,7 +87,8 @@ test("It maps projects including branches and tags", async () => {
         id: "openapi.yml",
         name: "openapi.yml",
         url: "/api/blob/acme/foo-openapi/openapi.yml?ref=12345678",
-        editURL: "https://github.com/acme/foo-openapi/edit/main/openapi.yml"
+        editURL: "https://github.com/acme/foo-openapi/edit/main/openapi.yml",
+        isDefault: false
       }],
       url: "https://github.com/acme/foo-openapi/tree/main",
       isDefault: true
@@ -98,7 +99,8 @@ test("It maps projects including branches and tags", async () => {
         id: "openapi.yml",
         name: "openapi.yml",
         url: "/api/blob/acme/foo-openapi/openapi.yml?ref=12345678",
-        editURL: "https://github.com/acme/foo-openapi/edit/1.0/openapi.yml"
+        editURL: "https://github.com/acme/foo-openapi/edit/1.0/openapi.yml",
+        isDefault: false
       }],
       url: "https://github.com/acme/foo-openapi/tree/1.0",
       isDefault: false
@@ -195,17 +197,20 @@ test("It supports multiple OpenAPI specifications on a branch", async () => {
         id: "foo-service.yml",
         name: "foo-service.yml",
         url: "/api/blob/acme/foo-openapi/foo-service.yml?ref=12345678",
-        editURL: "https://github.com/acme/foo-openapi/edit/main/foo-service.yml"
+        editURL: "https://github.com/acme/foo-openapi/edit/main/foo-service.yml",
+        isDefault: false
       }, {
         id: "bar-service.yml",
         name: "bar-service.yml",
         url: "/api/blob/acme/foo-openapi/bar-service.yml?ref=12345678",
-        editURL: "https://github.com/acme/foo-openapi/edit/main/bar-service.yml"
+        editURL: "https://github.com/acme/foo-openapi/edit/main/bar-service.yml",
+        isDefault: false
       }, {
         id: "baz-service.yml",
         name: "baz-service.yml",
         url: "/api/blob/acme/foo-openapi/baz-service.yml?ref=12345678",
-        editURL: "https://github.com/acme/foo-openapi/edit/main/baz-service.yml"
+        editURL: "https://github.com/acme/foo-openapi/edit/main/baz-service.yml",
+        isDefault: false
       }],
       url: "https://github.com/acme/foo-openapi/tree/main",
       isDefault: true
@@ -216,7 +221,8 @@ test("It supports multiple OpenAPI specifications on a branch", async () => {
         id: "openapi.yml",
         name: "openapi.yml",
         url: "/api/blob/acme/foo-openapi/openapi.yml?ref=12345678",
-        editURL: "https://github.com/acme/foo-openapi/edit/1.0/openapi.yml"
+        editURL: "https://github.com/acme/foo-openapi/edit/1.0/openapi.yml",
+        isDefault: false
       }],
       url: "https://github.com/acme/foo-openapi/tree/1.0",
       isDefault: false
@@ -749,11 +755,13 @@ test("It adds remote versions from the project configuration", async () => {
     specifications: [{
       id: "huey",
       name: "Huey",
-      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/huey.yml" })}`
+      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/huey.yml" })}`,
+      isDefault: false
     }, {
       id: "dewey",
       name: "Dewey",
-      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/dewey.yml" })}`
+      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/dewey.yml" })}`,
+      isDefault: false
     }]
   }, {
     id: "bobby",
@@ -762,7 +770,8 @@ test("It adds remote versions from the project configuration", async () => {
     specifications: [{
       id: "louie",
       name: "Louie",
-      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/louie.yml" })}`
+      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/louie.yml" })}`,
+      isDefault: false
     }]
   }])
 })
@@ -816,7 +825,8 @@ test("It modifies ID of remote version if the ID already exists", async () => {
       id: "openapi.yml",
       name: "openapi.yml",
       url: "/api/blob/acme/foo-openapi/openapi.yml?ref=12345678",
-      editURL: "https://github.com/acme/foo-openapi/edit/bar/openapi.yml"
+      editURL: "https://github.com/acme/foo-openapi/edit/bar/openapi.yml",
+      isDefault: false
     }]
   }, {
     id: "bar1",
@@ -825,7 +835,8 @@ test("It modifies ID of remote version if the ID already exists", async () => {
     specifications: [{
       id: "baz",
       name: "Baz",
-      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/baz.yml" })}`
+      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/baz.yml" })}`,
+      isDefault: false
     }]
   }, {
     id: "bar2",
@@ -834,7 +845,8 @@ test("It modifies ID of remote version if the ID already exists", async () => {
     specifications: [{
       id: "hello",
       name: "Hello",
-      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/hello.yml" })}`
+      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/hello.yml" })}`,
+      isDefault: false
     }]
   }])
 })
@@ -877,7 +889,8 @@ test("It lets users specify the ID of a remote version", async () => {
     specifications: [{
       id: "baz",
       name: "Baz",
-      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/baz.yml" })}`
+      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/baz.yml" })}`,
+      isDefault: false
     }]
   }])
 })
@@ -920,7 +933,168 @@ test("It lets users specify the ID of a remote specification", async () => {
     specifications: [{
       id: "some-spec",
       name: "Baz",
-      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/baz.yml" })}`
+      url: `/api/remotes/${base64RemoteConfigEncoder.encode({ url: "https://example.com/baz.yml" })}`,
+      isDefault: false
     }]
   }])
 })
+
+test("It sets isDefault on the correct specification based on defaultSpecificationName in config", async () => {
+  const sut = new GitHubProjectDataSource({
+    repositoryNameSuffix: "-openapi",
+    repositoryDataSource: {
+      async getRepositories() {
+        return [{
+          owner: "acme",
+          name: "foo-openapi",
+          defaultBranchRef: {
+            id: "12345678",
+            name: "main"
+          },
+          configYml: {
+            text: `
+            defaultSpecificationName: bar-service.yml
+            remoteVersions:
+              - name: Bar
+                specifications:
+                - id: some-spec
+                  name: Baz
+                  url: https://example.com/baz.yml
+            `
+          },
+          branches: [{
+            id: "12345678",
+            name: "main",
+            files: [
+              { name: "foo-service.yml" },
+              { name: "bar-service.yml" },
+              { name: "baz-service.yml" }
+            ]
+          }],
+          tags: []
+        }]
+      }
+    },
+    encryptionService: noopEncryptionService,
+    remoteConfigEncoder: base64RemoteConfigEncoder
+  })
+  const projects = await sut.getProjects()
+  const specs = projects[0].versions[0].specifications
+  expect(specs.find(s => s.name === "bar-service.yml")!.isDefault).toBe(true)
+  expect(specs.find(s => s.name === "foo-service.yml")!.isDefault).toBe(false)
+  expect(specs.find(s => s.name === "baz-service.yml")!.isDefault).toBe(false)
+  expect(projects[0].versions[1].specifications.find(s => s.name === "Baz")!.isDefault).toBe(false)
+})
+
+test("It sets a remote specification as the default if specified", async () => {
+  const sut = new GitHubProjectDataSource({
+    repositoryNameSuffix: "-openapi",
+    repositoryDataSource: {
+      async getRepositories() {
+        return [{
+          owner: "acme",
+          name: "foo-openapi",
+          defaultBranchRef: {
+            id: "12345678",
+            name: "main"
+          },
+          configYaml: {
+            text: `
+            defaultSpecificationName: Baz
+            remoteVersions:
+              - name: Bar
+                specifications:
+                - id: some-spec
+                  name: Baz
+                  url: https://example.com/baz.yml
+                - id: another-spec
+                  name: Qux
+                  url: https://example.com/qux.yml
+            `
+          },
+          branches: [],
+          tags: []
+        }]
+      }
+    },
+    encryptionService: noopEncryptionService,
+    remoteConfigEncoder: base64RemoteConfigEncoder
+  })
+  const projects = await sut.getProjects()
+  const remoteSpecs = projects[0].versions[0].specifications
+  expect(remoteSpecs.find(s => s.id === "some-spec")!.isDefault).toBe(true)
+  expect(remoteSpecs.find(s => s.id === "another-spec")!.isDefault).toBe(false)
+})
+
+
+test("It sets isDefault to false for all specifications if defaultSpecificationName is not set", async () => {
+  const sut = new GitHubProjectDataSource({
+    repositoryNameSuffix: "-openapi",
+    repositoryDataSource: {
+      async getRepositories() {
+        return [{
+          owner: "acme",
+          name: "foo-openapi",
+          defaultBranchRef: {
+            id: "12345678",
+            name: "main"
+          },
+          configYml: {
+            text: ``
+          },
+          branches: [{
+            id: "12345678",
+            name: "main",
+            files: [
+              { name: "foo-service.yml" },
+              { name: "bar-service.yml" },
+              { name: "baz-service.yml" }
+            ]
+          }],
+          tags: []
+        }]
+      }
+    },
+    encryptionService: noopEncryptionService,
+    remoteConfigEncoder: base64RemoteConfigEncoder
+  })
+  const projects = await sut.getProjects()
+  const specs = projects[0].versions[0].specifications
+  expect(specs.every(s => s.isDefault === false)).toBe(true)
+})
+
+test("It silently ignores defaultSpecificationName if no matching spec is found", async () => {
+  const sut = new GitHubProjectDataSource({
+    repositoryNameSuffix: "-openapi",
+    repositoryDataSource: {
+      async getRepositories() {
+        return [{
+          owner: "acme",
+          name: "foo-openapi",
+          defaultBranchRef: {
+            id: "12345678",
+            name: "main"
+          },
+          configYml: {
+            text: `defaultSpecificationName: non-existent.yml`
+          },
+          branches: [{
+            id: "12345678",
+            name: "main",
+            files: [
+              { name: "foo-service.yml" },
+              { name: "bar-service.yml" },
+              { name: "baz-service.yml" }
+            ]
+          }],
+          tags: []
+        }]
+      }
+    },
+    encryptionService: noopEncryptionService,
+    remoteConfigEncoder: base64RemoteConfigEncoder
+  })
+  const projects = await sut.getProjects()
+  const specs = projects[0].versions[0].specifications
+  expect(specs.every(s => s.isDefault === false)).toBe(true)
+})
diff --git a/src/features/projects/data/GitHubProjectDataSource.ts b/src/features/projects/data/GitHubProjectDataSource.ts
index dc6de577..acc33ed5 100644
--- a/src/features/projects/data/GitHubProjectDataSource.ts
+++ b/src/features/projects/data/GitHubProjectDataSource.ts
@@ -65,6 +65,7 @@ export default class GitHubProjectDataSource implements IProjectDataSource {
     ).filter(version => {
       return version.specifications.length > 0
     })
+    .map(version => this.setDefaultSpecification(version, config?.defaultSpecificationName));
     const defaultName = repository.name.replace(new RegExp(this.repositoryNameSuffix + "$"), "")
     return {
       id: `${repository.owner}-${defaultName}`,
@@ -130,7 +131,8 @@ export default class GitHubProjectDataSource implements IProjectDataSource {
           path: file.name,
           ref: ref.id
         }),
-        editURL: `https://github.com/${ownerName}/${repositoryName}/edit/${ref.name}/${file.name}`
+        editURL: `https://github.com/${ownerName}/${repositoryName}/edit/${ref.name}/${file.name}`,
+        isDefault: false // initial value
       }
     })
     return {
@@ -187,7 +189,8 @@ export default class GitHubProjectDataSource implements IProjectDataSource {
         return {
           id: this.makeURLSafeID((e.id || e.name).toLowerCase()),
           name: e.name,
-          url: `/api/remotes/${encodedRemoteConfig}`
+          url: `/api/remotes/${encodedRemoteConfig}`,
+          isDefault: false // initial value
         };
       })
       versions.push({
@@ -246,4 +249,14 @@ export default class GitHubProjectDataSource implements IProjectDataSource {
       return undefined
     }
   }
+
+  private setDefaultSpecification(version: Version, defaultSpecificationName?: string): Version {
+    return {
+      ...version,
+      specifications: version.specifications.map(spec => ({
+        ...spec,
+        isDefault: spec.name === defaultSpecificationName
+      }))
+    }
+  }
 }
diff --git a/src/features/projects/data/useProjectSelection.ts b/src/features/projects/data/useProjectSelection.ts
index 2ff26e96..de8327b4 100644
--- a/src/features/projects/data/useProjectSelection.ts
+++ b/src/features/projects/data/useProjectSelection.ts
@@ -4,7 +4,13 @@ import NProgress from "nprogress"
 import { useRouter, usePathname } from "next/navigation"
 import { useContext } from "react"
 import { ProjectsContext } from "@/common"
-import { Project, ProjectNavigator, getProjectSelectionFromPath } from "../domain"
+import {
+  Project,
+  ProjectNavigator,
+  getProjectSelectionFromPath,
+  getDefaultSpecification
+  
+} from "../domain"
 
 export default function useProjectSelection() {
   const router = useRouter()
@@ -29,7 +35,7 @@ export default function useProjectSelection() {
     },
     selectProject: (project: Project) => {
       const version = project.versions[0]
-      const specification = version.specifications[0]
+      const specification = getDefaultSpecification(version)
       NProgress.start()
       projectNavigator.navigate(
         project.owner,
diff --git a/src/features/projects/domain/IProjectConfig.ts b/src/features/projects/domain/IProjectConfig.ts
index 08e27f7c..34cf660c 100644
--- a/src/features/projects/domain/IProjectConfig.ts
+++ b/src/features/projects/domain/IProjectConfig.ts
@@ -20,6 +20,7 @@ export const ProjectConfigRemoteVersionSchema = z.object({
 export const IProjectConfigSchema = z.object({
   name: z.coerce.string().optional(),
   image: z.string().optional(),
+  defaultSpecificationName: z.string().optional(),
   remoteVersions: ProjectConfigRemoteVersionSchema.array().optional()
 })
 
diff --git a/src/features/projects/domain/OpenApiSpecification.ts b/src/features/projects/domain/OpenApiSpecification.ts
index 32ed1012..b0c3bfa5 100644
--- a/src/features/projects/domain/OpenApiSpecification.ts
+++ b/src/features/projects/domain/OpenApiSpecification.ts
@@ -4,7 +4,8 @@ export const OpenApiSpecificationSchema = z.object({
   id: z.string(),
   name: z.string(),
   url: z.string(),
-  editURL: z.string().optional()
+  editURL: z.string().optional(),
+  isDefault: z.boolean()
 })
 
 type OpenApiSpecification = z.infer<typeof OpenApiSpecificationSchema>
diff --git a/src/features/projects/domain/ProjectNavigator.ts b/src/features/projects/domain/ProjectNavigator.ts
index aa87c239..e3d03217 100644
--- a/src/features/projects/domain/ProjectNavigator.ts
+++ b/src/features/projects/domain/ProjectNavigator.ts
@@ -1,4 +1,5 @@
 import Project from "./Project"
+import { getDefaultSpecification } from "./Version"
 
 interface IPathnameReader {
   readonly pathname: string
@@ -36,8 +37,8 @@ export default class ProjectNavigator {
     if (candidateSpecification) {
       this.router.push(`/${project.owner}/${project.name}/${newVersion.id}/${candidateSpecification.id}`)
     } else {
-      const firstSpecification = newVersion.specifications[0]
-      this.router.push(`/${project.owner}/${project.name}/${newVersion.id}/${firstSpecification.id}`)
+      const defaultOrFirstSpecification = getDefaultSpecification(newVersion)
+      this.router.push(`/${project.owner}/${project.name}/${newVersion.id}/${defaultOrFirstSpecification.id}`)
     }
   }
   
diff --git a/src/features/projects/domain/Version.ts b/src/features/projects/domain/Version.ts
index 2eee9225..f6b69989 100644
--- a/src/features/projects/domain/Version.ts
+++ b/src/features/projects/domain/Version.ts
@@ -12,3 +12,7 @@ export const VersionSchema = z.object({
 type Version = z.infer<typeof VersionSchema>
 
 export default Version
+
+export function getDefaultSpecification(version: Version) {
+  return version.specifications.find((spec) => spec.isDefault) || version.specifications[0]
+}
diff --git a/src/features/projects/domain/getProjectSelectionFromPath.ts b/src/features/projects/domain/getProjectSelectionFromPath.ts
index b18c405c..dfa5497e 100644
--- a/src/features/projects/domain/getProjectSelectionFromPath.ts
+++ b/src/features/projects/domain/getProjectSelectionFromPath.ts
@@ -1,5 +1,5 @@
 import Project from "./Project"
-import Version from "./Version"
+import Version, { getDefaultSpecification } from "./Version"
 import OpenApiSpecification from "./OpenApiSpecification"
 
 export default function getProjectSelectionFromPath({
@@ -61,7 +61,7 @@ export default function getProjectSelectionFromPath({
   if (specificationId && !didMoveSpecificationIdToVersionId) {
     specification = version.specifications.find(e => e.id == specificationId)
   } else if (version.specifications.length > 0) {
-    specification = version.specifications[0]
+    specification = getDefaultSpecification(version)
   }
   return { project, version, specification }
 }
diff --git a/src/features/projects/domain/index.ts b/src/features/projects/domain/index.ts
index 2b3f10cf..2bf08445 100644
--- a/src/features/projects/domain/index.ts
+++ b/src/features/projects/domain/index.ts
@@ -16,3 +16,4 @@ export { default as ProjectNavigator } from "./ProjectNavigator"
 export { default as ProjectRepository } from "./ProjectRepository"
 export { default as updateWindowTitle } from "./updateWindowTitle"
 export type { default as Version } from "./Version"
+export { getDefaultSpecification } from "./Version"