diff --git a/modules/openapi-generator/src/main/resources/swift5/modelOneOf.mustache b/modules/openapi-generator/src/main/resources/swift5/modelOneOf.mustache
index 312cda2f1ccd..4bf1ce40276d 100644
--- a/modules/openapi-generator/src/main/resources/swift5/modelOneOf.mustache
+++ b/modules/openapi-generator/src/main/resources/swift5/modelOneOf.mustache
@@ -14,13 +14,43 @@
             try container.encode(value)
         {{/oneOf}}
         {{#oneOfUnknownDefaultCase}}
-        case unknownDefaultOpenApi(let type):
+        case .unknownDefaultOpenApi:
             try container.encodeNil()
         {{/oneOfUnknownDefaultCase}}
         }
     }
 
+    {{#discriminator}}
+    private enum DiscriminatorCodingKey: String, CodingKey {
+        case {{discriminator.propertyName}} = "{{discriminator.propertyBaseName}}"
+    }
+    {{/discriminator}}
+
     public init(from decoder: Decoder) throws {
+        {{#discriminator}}
+        let keyedContainer = try decoder.container(keyedBy: DiscriminatorCodingKey.self)
+        let discriminatorValue = try keyedContainer.decode(String.self, forKey: .{{discriminator.propertyName}})
+
+        switch discriminatorValue {
+        {{#discriminator.mappedModels}}
+        case "{{mappingName}}":
+            self = .type{{modelName}}(try {{modelName}}(from: decoder))
+        {{/discriminator.mappedModels}}
+        default:
+            {{#oneOfUnknownDefaultCase}}
+            self = .unknownDefaultOpenApi
+            {{/oneOfUnknownDefaultCase}}
+            {{^oneOfUnknownDefaultCase}}
+            throw DecodingError.dataCorrupted(
+                DecodingError.Context(
+                    codingPath: decoder.codingPath,
+                    debugDescription: "Unknown discriminator value '\(discriminatorValue)' for {{classname}}"
+                )
+            )
+            {{/oneOfUnknownDefaultCase}}
+        }
+        {{/discriminator}}
+        {{^discriminator}}
         let container = try decoder.singleValueContainer()
         {{#oneOf}}
         {{#-first}}
@@ -39,5 +69,6 @@
             throw DecodingError.typeMismatch(Self.Type.self, .init(codingPath: decoder.codingPath, debugDescription: "Unable to decode instance of {{classname}}"))
             {{/oneOfUnknownDefaultCase}}
         }
+        {{/discriminator}}
     }
 }
diff --git a/modules/openapi-generator/src/main/resources/swift6/modelOneOf.mustache b/modules/openapi-generator/src/main/resources/swift6/modelOneOf.mustache
index 06205f18249c..c49411f3309d 100644
--- a/modules/openapi-generator/src/main/resources/swift6/modelOneOf.mustache
+++ b/modules/openapi-generator/src/main/resources/swift6/modelOneOf.mustache
@@ -14,13 +14,43 @@
             try container.encode(value)
         {{/oneOf}}
         {{#oneOfUnknownDefaultCase}}
-        case unknownDefaultOpenApi(let type):
+        case .unknownDefaultOpenApi:
             try container.encodeNil()
         {{/oneOfUnknownDefaultCase}}
         }
     }
 
+    {{#discriminator}}
+    private enum DiscriminatorCodingKey: String, CodingKey {
+        case {{discriminator.propertyName}} = "{{discriminator.propertyBaseName}}"
+    }
+    {{/discriminator}}
+
     public init(from decoder: Decoder) throws {
+        {{#discriminator}}
+        let keyedContainer = try decoder.container(keyedBy: DiscriminatorCodingKey.self)
+        let discriminatorValue = try keyedContainer.decode(String.self, forKey: .{{discriminator.propertyName}})
+
+        switch discriminatorValue {
+        {{#discriminator.mappedModels}}
+        case "{{mappingName}}":
+            self = .type{{#transformArrayType}}{{modelName}}{{/transformArrayType}}(try {{modelName}}(from: decoder))
+        {{/discriminator.mappedModels}}
+        default:
+            {{#oneOfUnknownDefaultCase}}
+            self = .unknownDefaultOpenApi
+            {{/oneOfUnknownDefaultCase}}
+            {{^oneOfUnknownDefaultCase}}
+            throw DecodingError.dataCorrupted(
+                DecodingError.Context(
+                    codingPath: decoder.codingPath,
+                    debugDescription: "Unknown discriminator value '\(discriminatorValue)' for {{classname}}"
+                )
+            )
+            {{/oneOfUnknownDefaultCase}}
+        }
+        {{/discriminator}}
+        {{^discriminator}}
         let container = try decoder.singleValueContainer()
         {{#oneOf}}
         {{#-first}}
@@ -39,5 +69,6 @@
             throw DecodingError.typeMismatch(Self.Type.self, .init(codingPath: decoder.codingPath, debugDescription: "Unable to decode instance of {{classname}}"))
             {{/oneOfUnknownDefaultCase}}
         }
+        {{/discriminator}}
     }
 }
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/swift5/Swift5ClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/swift5/Swift5ClientCodegenTest.java
index 8ce28b3467e4..712b86e1e2e9 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/swift5/Swift5ClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/swift5/Swift5ClientCodegenTest.java
@@ -317,4 +317,42 @@ public void oneOfFormParameterTest() {
 
     }
 
+    @Test(description = "test oneOf with discriminator generates discriminator-first decoding", enabled = true)
+    public void oneOfDiscriminatorFirstDecodingTest() throws IOException {
+        Path target = Files.createTempDirectory("test");
+        File output = target.toFile();
+        try {
+            final CodegenConfigurator configurator = new CodegenConfigurator()
+                    .setGeneratorName("swift5")
+                    .setInputSpec("src/test/resources/3_0/oneOfDiscriminator.yaml")
+                    .setOutputDir(target.toAbsolutePath().toString());
+
+            final ClientOptInput clientOptInput = configurator.toClientOptInput();
+            DefaultGenerator generator = new DefaultGenerator(false);
+            generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
+            generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "false");
+            generator.setGeneratorPropertyDefault(CodegenConstants.SUPPORTING_FILES, "false");
+
+            List<File> files = generator.opts(clientOptInput).generate();
+
+            File modelFile = files.stream()
+                    .filter(f -> f.getName().equals("FruitOneOfEnumMappingDisc.swift"))
+                    .findFirst()
+                    .orElseThrow(() -> new RuntimeException("FruitOneOfEnumMappingDisc.swift not found"));
+
+            String content = Files.readString(modelFile.toPath());
+
+            // Verify discriminator-first decoding pattern
+            Assert.assertTrue(content.contains("private enum DiscriminatorCodingKey: String, CodingKey"));
+            Assert.assertTrue(content.contains("let keyedContainer = try decoder.container(keyedBy: DiscriminatorCodingKey.self)"));
+            Assert.assertTrue(content.contains("switch discriminatorValue"));
+            Assert.assertTrue(content.contains("case \"APPLE\":"));
+            Assert.assertTrue(content.contains("self = .typeAppleOneOfEnumMappingDisc(try AppleOneOfEnumMappingDisc(from: decoder))"));
+            Assert.assertFalse(content.contains("if let value = try? container.decode(AppleOneOfEnumMappingDisc.self)"));
+
+        } finally {
+            output.deleteOnExit();
+        }
+    }
+
 }
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/swift6/Swift6ClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/swift6/Swift6ClientCodegenTest.java
index 4fcfe0d9728f..1bba4234b30f 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/swift6/Swift6ClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/swift6/Swift6ClientCodegenTest.java
@@ -363,4 +363,42 @@ public void oneOfArrayTypeNamesTest() throws IOException {
             output.deleteOnExit();
         }
     }
+
+    @Test(description = "test oneOf with discriminator generates discriminator-first decoding", enabled = true)
+    public void oneOfDiscriminatorFirstDecodingTest() throws IOException {
+        Path target = Files.createTempDirectory("test");
+        File output = target.toFile();
+        try {
+            final CodegenConfigurator configurator = new CodegenConfigurator()
+                    .setGeneratorName("swift6")
+                    .setInputSpec("src/test/resources/3_0/oneOfDiscriminator.yaml")
+                    .setOutputDir(target.toAbsolutePath().toString());
+
+            final ClientOptInput clientOptInput = configurator.toClientOptInput();
+            DefaultGenerator generator = new DefaultGenerator(false);
+            generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
+            generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "false");
+            generator.setGeneratorPropertyDefault(CodegenConstants.SUPPORTING_FILES, "false");
+
+            List<File> files = generator.opts(clientOptInput).generate();
+
+            File modelFile = files.stream()
+                    .filter(f -> f.getName().equals("FruitOneOfEnumMappingDisc.swift"))
+                    .findFirst()
+                    .orElseThrow(() -> new RuntimeException("FruitOneOfEnumMappingDisc.swift not found"));
+
+            String content = Files.readString(modelFile.toPath());
+
+            // Verify discriminator-first decoding pattern
+            Assert.assertTrue(content.contains("private enum DiscriminatorCodingKey: String, CodingKey"));
+            Assert.assertTrue(content.contains("let keyedContainer = try decoder.container(keyedBy: DiscriminatorCodingKey.self)"));
+            Assert.assertTrue(content.contains("switch discriminatorValue"));
+            Assert.assertTrue(content.contains("case \"APPLE\":"));
+            Assert.assertTrue(content.contains("self = .typeAppleOneOfEnumMappingDisc(try AppleOneOfEnumMappingDisc(from: decoder))"));
+            Assert.assertFalse(content.contains("if let value = try? container.decode(AppleOneOfEnumMappingDisc.self)"));
+
+        } finally {
+            output.deleteOnExit();
+        }
+    }
 }
diff --git a/samples/client/petstore/swift5/oneOf/PetstoreClient/Classes/OpenAPIs/Models/Fruit.swift b/samples/client/petstore/swift5/oneOf/PetstoreClient/Classes/OpenAPIs/Models/Fruit.swift
index 0a7c58c949d8..ca95d10ffb06 100644
--- a/samples/client/petstore/swift5/oneOf/PetstoreClient/Classes/OpenAPIs/Models/Fruit.swift
+++ b/samples/client/petstore/swift5/oneOf/PetstoreClient/Classes/OpenAPIs/Models/Fruit.swift
@@ -27,6 +27,7 @@ public enum Fruit: Codable, JSONEncodable, Hashable {
         }
     }
 
+
     public init(from decoder: Decoder) throws {
         let container = try decoder.singleValueContainer()
         if let value = try? container.decode(Apple.self) {
diff --git a/samples/client/petstore/swift6/oneOf/PetstoreClient/Classes/OpenAPIs/Models/Fruit.swift b/samples/client/petstore/swift6/oneOf/PetstoreClient/Classes/OpenAPIs/Models/Fruit.swift
index 7d60ea96189a..20c9683e14fb 100644
--- a/samples/client/petstore/swift6/oneOf/PetstoreClient/Classes/OpenAPIs/Models/Fruit.swift
+++ b/samples/client/petstore/swift6/oneOf/PetstoreClient/Classes/OpenAPIs/Models/Fruit.swift
@@ -24,6 +24,7 @@ public enum Fruit: Sendable, Codable, ParameterConvertible, Hashable {
         }
     }
 
+
     public init(from decoder: Decoder) throws {
         let container = try decoder.singleValueContainer()
         if let value = try? container.decode(Apple.self) {