diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4035a2a..2bfc74a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@
 - [#116](https://github.com/clojure-emacs/clojure-ts-mode/pull/116): Extend built-in completion to complete all imported symbols from an `ns`
   form.
 - Add documentation and bug reporting commands from `clojure-mode`.
+- Add some ns manipulation functions from `clojure-mode`.
 
 ## 0.5.1 (2025-06-17)
 
diff --git a/clojure-ts-mode.el b/clojure-ts-mode.el
index 0cbf862..bcb0107 100644
--- a/clojure-ts-mode.el
+++ b/clojure-ts-mode.el
@@ -58,6 +58,7 @@
 (require 'treesit)
 (require 'align)
 (require 'subr-x)
+(require 'project)
 
 (declare-function treesit-parser-create "treesit.c")
 (declare-function treesit-node-eq "treesit.c")
@@ -266,6 +267,52 @@ values like this:
   :safe #'booleanp
   :type 'boolean)
 
+(defcustom clojure-ts-build-tool-files
+  '("project.clj"      ; Leiningen
+    "build.boot"       ; Boot
+    "build.gradle"     ; Gradle
+    "build.gradle.kts" ; Gradle
+    "deps.edn"         ; Clojure CLI (a.k.a. tools.deps)
+    "shadow-cljs.edn"  ; shadow-cljs
+    "bb.edn"           ; babashka
+    "nbb.edn"          ; nbb
+    "basilisp.edn"     ; Basilisp (Python)
+    )
+  "A list of files, which identify a Clojure project's root."
+  :type '(repeat string)
+  :package-version '(clojure-ts-mode . "0.6.0")
+  :safe (lambda (value)
+          (and (listp value)
+               (cl-every 'stringp value))))
+
+(defcustom clojure-ts-cache-project-dir t
+  "Whether to cache the results of `clojure-ts-project-dir'."
+  :type 'boolean
+  :safe #'booleanp
+  :package-version '(clojure-ts-mode . "0.6.0"))
+
+(defcustom clojure-ts-cache-ns nil
+  "Whether to cache the results of `clojure-ts-find-ns'.
+
+Note that this won't work well in buffers with multiple namespace
+declarations (which rarely occur in practice) and you'll have to
+invalidate this manually after changing the ns for a buffer.  If you
+update the ns using `clojure-ts-update-ns' the cached value will be
+updated automatically."
+  :type 'boolean
+  :safe #'booleanp
+  :package-version '(clojure-ts-mode . "0.6.0"))
+
+(defcustom clojure-ts-directory-prefixes
+  '("^\\(?:[^/]+/\\)*clj[csxd]*/")
+  "A list of directory prefixes used by `clojure-expected-ns'.
+The prefixes are used to generate the correct namespace."
+  :type '(repeat string)
+  :package-version '(clojure-mode . "0.6.0")
+  :safe (lambda (value)
+          (and (listp value)
+               (cl-every 'stringp value))))
+
 (defvar clojure-ts-mode-remappings
   '((clojure-mode . clojure-ts-mode)
     (clojurescript-mode . clojure-ts-clojurescript-mode)
@@ -2689,6 +2736,146 @@ The command will prompt you to select one of the available sections."
     map)
   "Keymap for `clojure-ts-mode'.")
 
+;;; Project helpers
+
+(defun clojure-ts-project-root-path (&optional dir-name)
+  "Return the absolute path to the project's root directory.
+
+Uses `default-directory' if DIR-NAME is nil.  Return nil if not inside
+of a project.
+
+NOTE: this function uses `project.el' internally, so if Clojure source
+is located in a non-Clojure project, but still under version control,
+the root of the project will be returned."
+  (let ((default-directory (or dir-name default-directory))
+        (project-vc-extra-root-markers clojure-ts-build-tool-files))
+    (expand-file-name (project-root (project-current)))))
+
+(defcustom clojure-ts-project-root-function #'clojure-ts-project-root-path
+  "Function to locate Clojure project root directory."
+  :type 'function
+  :risky t
+  :package-version '(clojure-ts-mode . "0.6.0"))
+
+(defvar-local clojure-ts-cached-project-dir nil
+  "A project dir cache used to speed up related operations.")
+
+(defun clojure-ts-project-dir (&optional dir-name)
+  "Return an absolute path to the project's root directory.
+
+Call is delegated down to `clojure-ts-project-root-function' with
+optional DIR-NAME as argument.
+
+When `clojure-ts-cache-project-dir' is non-nil, the result of the
+command is cached in a buffer local variable
+`clojure-ts-cached-project-dir'."
+  (let ((project-dir (or clojure-ts-cached-project-dir
+                         (funcall clojure-ts-project-root-function dir-name))))
+    (when (and clojure-ts-cache-project-dir
+               (derived-mode-p 'clojure-ts-mode)
+               (not clojure-ts-cached-project-dir))
+      (setq-local clojure-ts-cached-project-dir project-dir))
+    project-dir))
+
+(defun clojure-ts-project-relative-path (path)
+  "Denormalize PATH by making it relative to the project root."
+  (file-relative-name path (clojure-ts-project-dir)))
+
+;;; ns manipulation
+
+(defun clojure-ts-expected-ns (&optional path)
+  "Return the namespace matching PATH.
+
+PATH is expected to be an absolute file path.
+
+If PATH is nil, use the path to the file backing the current buffer."
+  (when-let* ((path (or path (when-let* ((buf-file-name (buffer-file-name)))
+                               (file-truename buf-file-name))))
+              (relative (clojure-ts-project-relative-path path))
+              ;; Drop prefix from ns for projects with structure
+              ;; src/{clj,cljs,cljc}
+              (without-prefix (seq-reduce (lambda (acc regex)
+                                            (replace-regexp-in-string regex "" acc))
+                                          clojure-ts-directory-prefixes
+                                          relative)))
+    (thread-last without-prefix
+                 (file-name-sans-extension)
+                 (string-replace "_" "-")
+                 (string-replace "/" "."))))
+
+(defvar-local clojure-ts-expected-ns-function nil
+  "The function used to determine the expected namespace of a file.
+
+`clojure-ts-mode' ships a basic function named `clojure-ts-expected-ns'
+that does basic heuristics to figure this out.  It can be redefined by
+other packages to provide a more complex version.")
+
+(defun clojure-ts-insert-ns-form-at-point ()
+  "Insert a namespace form at point."
+  (interactive)
+  (insert (format "(ns %s)" (funcall clojure-ts-expected-ns-function))))
+
+(defun clojure-ts-insert-ns-form ()
+  "Insert a namespace form at the beginning of the buffer."
+  (interactive)
+  (widen)
+  (goto-char (point-min))
+  (clojure-ts-insert-ns-form-at-point))
+
+(defvar-local clojure-ts-cached-ns nil
+  "A buffer ns cache to speed up ns-related operations.")
+
+(defconst clojure-ts--find-ns-query
+  (treesit-query-compile
+   'clojure
+   '(((source (list_lit
+               :anchor [(comment) (meta_lit) (old_meta_lit)] :*
+               :anchor (sym_lit name: (sym_name) @ns)
+               :anchor [(comment) (meta_lit) (old_meta_lit)] :*
+               :anchor (sym_lit name: (sym_name) @ns-name)))
+      (:equal @ns "ns"))
+     ((source (list_lit
+               :anchor [(comment) (meta_lit) (old_meta_lit)] :*
+               :anchor (sym_lit name: (sym_name) @in-ns)
+               :anchor [(comment) (meta_lit) (old_meta_lit)] :*
+               :anchor (quoting_lit
+                        :anchor (sym_lit name: (sym_name) @ns-name))))
+      (:equal @in-ns "in-ns"))))
+  "Compiled Tree-sitter query to capture Clojure ns node.")
+
+(defun clojure-ts-find-ns ()
+  "Return the name of the current namespace."
+  (if (and clojure-ts-cache-ns clojure-ts-cached-ns)
+      clojure-ts-cached-ns
+    (when-let* ((nodes (treesit-query-capture 'clojure clojure-ts--find-ns-query))
+                (ns-name-node (cdr (assoc 'ns-name nodes)))
+                (ns-name (treesit-node-text ns-name-node t)))
+      (when clojure-ts-cache-ns
+        (setq-local clojure-ts-cached-ns ns-name))
+      ;; Set the match data, so the namespace could be easily replaced.
+      (let ((start (treesit-node-start ns-name-node))
+            (end (treesit-node-end ns-name-node)))
+        (set-match-data (list start end)))
+      ns-name)))
+
+(defun clojure-ts-update-ns ()
+  "Update the namespace of the current buffer.
+
+Useful if a file has been renamed."
+  (interactive)
+  (when-let* ((ns-name (funcall clojure-ts-expected-ns-function)))
+    (save-excursion
+      (save-match-data
+        (if (clojure-ts-find-ns)
+            (progn
+              ;; This relies on the match data, set by `clojure-ts-find-ns'
+              ;; function.
+              (replace-match ns-name nil nil nil 0)
+              (message "ns form updated to `%s'" ns-name)
+              (when clojure-ts-cache-ns
+                (setq-local clojure-ts-cached-ns ns-name)))
+          (user-error "Can't find ns form"))))))
+
 ;;; Completion
 
 (defconst clojure-ts--completion-query-defuns
@@ -2978,6 +3165,8 @@ REGEX-AVAILABLE."
                 outline-search-function #'treesit-outline-search
                 outline-level #'clojure-ts--outline-level))
 
+  (setq-local clojure-ts-expected-ns-function #'clojure-ts-expected-ns)
+
   (setq-local treesit-font-lock-settings
               (clojure-ts--font-lock-settings markdown-available regex-available))
   (setq-local treesit-font-lock-feature-list
@@ -3169,28 +3358,6 @@ Useful if you want to switch to the `clojure-mode's mode mappings."
         (add-to-list 'interpreter-mode-alist '("nbb" . clojure-ts-clojurescript-mode))))
   (message "Clojure TS Mode will not be activated as Tree-sitter support is missing."))
 
-(defvar clojure-ts--find-ns-query
-  (treesit-query-compile
-   'clojure
-   '(((source (list_lit
-               :anchor [(comment) (meta_lit) (old_meta_lit)] :*
-               :anchor (sym_lit name: (sym_name) @ns)
-               :anchor [(comment) (meta_lit) (old_meta_lit)] :*
-               :anchor (sym_lit name: (sym_name) @ns-name)))
-      (:equal @ns "ns"))
-     ((source (list_lit
-               :anchor [(comment) (meta_lit) (old_meta_lit)] :*
-               :anchor (sym_lit name: (sym_name) @in-ns)
-               :anchor [(comment) (meta_lit) (old_meta_lit)] :*
-               :anchor (quoting_lit
-                        :anchor (sym_lit name: (sym_name) @ns-name))))
-      (:equal @in-ns "in-ns")))))
-
-(defun clojure-ts-find-ns ()
-  "Return the name of the current namespace."
-  (let ((nodes (treesit-query-capture 'clojure clojure-ts--find-ns-query)))
-    (treesit-node-text (cdr (assoc 'ns-name nodes)) t)))
-
 (provide 'clojure-ts-mode)
 
 ;;; clojure-ts-mode.el ends here
diff --git a/test/clojure-ts-mode-util-test.el b/test/clojure-ts-mode-util-test.el
index 05b0fcc..32f9d29 100644
--- a/test/clojure-ts-mode-util-test.el
+++ b/test/clojure-ts-mode-util-test.el
@@ -21,13 +21,55 @@
 
 ;; The unit test suite of Clojure TS Mode
 
+;;; Code:
+
 (require 'clojure-ts-mode)
 (require 'buttercup)
+(require 'test-helper "test/test-helper")
 
 (describe "clojure-ts-mode-version"
   (it "should not be nil"
     (expect clojure-ts-mode-version)))
 
+(defvar clojure-ts-cache-project)
+
+(let ((project-dir "/home/user/projects/my-project/")
+      (clj-file-path "/home/user/projects/my-project/src/clj/my_project/my_ns/my_file.clj")
+      (project-relative-clj-file-path "src/clj/my_project/my_ns/my_file.clj")
+      (clj-file-ns "my-project.my-ns.my-file")
+      (clojure-ts-cache-project nil))
+
+  (describe "clojure-ts-project-root-path"
+    (it "nbb subdir"
+      (with-temp-dir temp-dir
+                     (let* ((bb-edn (expand-file-name "nbb.edn" temp-dir))
+                            (bb-edn-src (expand-file-name "src" temp-dir)))
+                       (write-region "{}" nil bb-edn)
+                       (make-directory bb-edn-src)
+                       (expect (expand-file-name (clojure-ts-project-dir bb-edn-src))
+                               :to-equal (file-name-as-directory temp-dir))))))
+
+  (describe "clojure-ts-project-relative-path"
+    (cl-letf (((symbol-function 'clojure-ts-project-dir) (lambda () project-dir)))
+      (expect (clojure-ts-project-relative-path clj-file-path)
+              :to-equal project-relative-clj-file-path)))
+
+  (describe "clojure-ts-expected-ns"
+    (it "should return the namespace matching a path"
+      (cl-letf (((symbol-function 'clojure-ts-project-relative-path)
+                 (lambda (&optional _current-buffer-file-name)
+                   project-relative-clj-file-path)))
+        (expect (clojure-ts-expected-ns clj-file-path)
+                :to-equal clj-file-ns)))
+
+    (it "should return the namespace even without a path"
+      (cl-letf (((symbol-function 'clojure-ts-project-relative-path)
+                 (lambda (&optional _current-buffer-file-name)
+                   project-relative-clj-file-path)))
+        (expect (let ((buffer-file-name clj-file-path))
+                  (clojure-ts-expected-ns))
+                :to-equal clj-file-ns)))))
+
 (describe "clojure-ts-find-ns"
   (it "should find common namespace declarations"
     (with-clojure-ts-buffer "(ns foo)"
diff --git a/test/samples/deps-project/deps.edn b/test/samples/deps-project/deps.edn
new file mode 100644
index 0000000..a29d91e
--- /dev/null
+++ b/test/samples/deps-project/deps.edn
@@ -0,0 +1 @@
+{:paths ["src/clj"]}
diff --git a/test/samples/deps-project/src/clj/hello-clj/world.clj b/test/samples/deps-project/src/clj/hello-clj/world.clj
new file mode 100644
index 0000000..e573fbb
--- /dev/null
+++ b/test/samples/deps-project/src/clj/hello-clj/world.clj
@@ -0,0 +1,8 @@
+(ns hello-clj.world
+  (:require
+   ;; This is a comment
+   [clojure.string :as str]
+   ;; Hello world
+   [clojure.math :as math])
+  (:import
+   (java.util.time Instant ZonedDateTime)))
diff --git a/test/samples/deps-project/src/clj/hello/world.clj b/test/samples/deps-project/src/clj/hello/world.clj
new file mode 100644
index 0000000..ee9b929
--- /dev/null
+++ b/test/samples/deps-project/src/clj/hello/world.clj
@@ -0,0 +1 @@
+(ns hello.world)
diff --git a/test/samples/refactoring.clj b/test/samples/refactoring.clj
index 5a87bf7..c2346ee 100644
--- a/test/samples/refactoring.clj
+++ b/test/samples/refactoring.clj
@@ -146,4 +146,4 @@
   clojure.lang.IPersistentMap
   (set-parameter [])
   (set-parameter [m ^PreparedStatement s i]
-    (.setObject| s i (->pgobject m))))
+    (.setObject s i (->pgobject m))))