diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4fc4e54e..8049cba3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -45,6 +45,7 @@
 
 ## Syntaxes
 
+- Add shebang-based detection for Tcl (`tclsh`, `wish`) and Expect (`expect`) scripts, see #3647 (@mvanhorn)
 - Change the URL of Zig submodule from GitHub to Codeberg, see #3519 (@sorairolake)
 - Don't color strings inside CSV files, to make it easier to tell which column they belong to, see #3521 (@keith-hall)
 - Add syntax highlighting support for COBOL, see #3584 (@adukhan99)
diff --git a/assets/patches/Tcl.sublime-syntax.patch b/assets/patches/Tcl.sublime-syntax.patch
new file mode 100644
index 00000000..487a1841
--- /dev/null
+++ b/assets/patches/Tcl.sublime-syntax.patch
@@ -0,0 +1,12 @@
+diff --git syntaxes/01_Packages/TCL/Tcl.sublime-syntax syntaxes/01_Packages/TCL/Tcl.sublime-syntax
+index 1234567..abcdefg 100644
+--- syntaxes/01_Packages/TCL/Tcl.sublime-syntax
++++ syntaxes/01_Packages/TCL/Tcl.sublime-syntax
+@@ -3,6 +3,7 @@
+ # http://www.sublimetext.com/docs/3/syntax.html
+ name: Tcl
+ file_extensions:
+   - tcl
++first_line_match: ^\#!.*\b(tclsh|wish|expect)\b
+ scope: source.tcl
+ variables:
diff --git a/tests/examples/regression_tests/issue_3647_expect b/tests/examples/regression_tests/issue_3647_expect
new file mode 100644
index 00000000..3786df69
--- /dev/null
+++ b/tests/examples/regression_tests/issue_3647_expect
@@ -0,0 +1,2 @@
+#!/usr/bin/expect -f
+set timeout 30
diff --git a/tests/examples/regression_tests/issue_3647_tclsh b/tests/examples/regression_tests/issue_3647_tclsh
new file mode 100644
index 00000000..0f4b3c5c
--- /dev/null
+++ b/tests/examples/regression_tests/issue_3647_tclsh
@@ -0,0 +1,2 @@
+#!/usr/bin/env tclsh
+puts "Hello from tclsh"
diff --git a/tests/examples/regression_tests/issue_3647_wish b/tests/examples/regression_tests/issue_3647_wish
new file mode 100644
index 00000000..8bfe4baf
--- /dev/null
+++ b/tests/examples/regression_tests/issue_3647_wish
@@ -0,0 +1,2 @@
+#!/usr/bin/wish
+button .b -text "Click"
diff --git a/tests/integration_tests.rs b/tests/integration_tests.rs
index 8ae4cfdd..432faed8 100644
--- a/tests/integration_tests.rs
+++ b/tests/integration_tests.rs
@@ -4202,3 +4202,36 @@ fn plain_without_diff_still_works() {
         .success()
         .stdout("line 1\nline 2 modified\nline 3\nline 4 added\n");
 }
+
+#[test]
+fn tcl_shebang_detection_tclsh() {
+    bat()
+        .arg("--color=always")
+        .arg("--style=plain")
+        .arg("--decorations=always")
+        .arg("regression_tests/issue_3647_tclsh")
+        .assert()
+        .success();
+}
+
+#[test]
+fn tcl_shebang_detection_wish() {
+    bat()
+        .arg("--color=always")
+        .arg("--style=plain")
+        .arg("--decorations=always")
+        .arg("regression_tests/issue_3647_wish")
+        .assert()
+        .success();
+}
+
+#[test]
+fn tcl_shebang_detection_expect() {
+    bat()
+        .arg("--color=always")
+        .arg("--style=plain")
+        .arg("--decorations=always")
+        .arg("regression_tests/issue_3647_expect")
+        .assert()
+        .success();
+}
diff --git a/tests/syntax-tests/highlighted/Tcl/expect_shebang b/tests/syntax-tests/highlighted/Tcl/expect_shebang
new file mode 100644
index 00000000..871eed6c
--- /dev/null
+++ b/tests/syntax-tests/highlighted/Tcl/expect_shebang
@@ -0,0 +1,7 @@
+#!/usr/bin/expect -f
+# Expect script detected via expect shebang
+set timeout 30
+spawn ssh user@host
+expect "password:"
+send "secret\r"
+expect eof
diff --git a/tests/syntax-tests/highlighted/Tcl/tclsh_shebang b/tests/syntax-tests/highlighted/Tcl/tclsh_shebang
new file mode 100644
index 00000000..5461f5f8
--- /dev/null
+++ b/tests/syntax-tests/highlighted/Tcl/tclsh_shebang
@@ -0,0 +1,7 @@
+#!/usr/bin/env tclsh
+# Tcl script detected via tclsh shebang
+puts "Hello from tclsh"
+set x 42
+if {$x > 0} {
+    puts "positive"
+}
diff --git a/tests/syntax-tests/highlighted/Tcl/wish_shebang b/tests/syntax-tests/highlighted/Tcl/wish_shebang
new file mode 100644
index 00000000..94fb971f
--- /dev/null
+++ b/tests/syntax-tests/highlighted/Tcl/wish_shebang
@@ -0,0 +1,5 @@
+#!/usr/bin/wish
+# Tk script detected via wish shebang
+package require Tk
+button .b -text "Click" -command {puts "clicked"}
+pack .b
diff --git a/tests/syntax-tests/source/Tcl/expect_shebang b/tests/syntax-tests/source/Tcl/expect_shebang
new file mode 100644
index 00000000..ef288ba8
--- /dev/null
+++ b/tests/syntax-tests/source/Tcl/expect_shebang
@@ -0,0 +1,7 @@
+#!/usr/bin/expect -f
+# Expect script detected via expect shebang
+set timeout 30
+spawn ssh user@host
+expect "password:"
+send "secret\r"
+expect eof
diff --git a/tests/syntax-tests/source/Tcl/tclsh_shebang b/tests/syntax-tests/source/Tcl/tclsh_shebang
new file mode 100644
index 00000000..08faa4d6
--- /dev/null
+++ b/tests/syntax-tests/source/Tcl/tclsh_shebang
@@ -0,0 +1,7 @@
+#!/usr/bin/env tclsh
+# Tcl script detected via tclsh shebang
+puts "Hello from tclsh"
+set x 42
+if {$x > 0} {
+    puts "positive"
+}
diff --git a/tests/syntax-tests/source/Tcl/wish_shebang b/tests/syntax-tests/source/Tcl/wish_shebang
new file mode 100644
index 00000000..690e73ef
--- /dev/null
+++ b/tests/syntax-tests/source/Tcl/wish_shebang
@@ -0,0 +1,5 @@
+#!/usr/bin/wish
+# Tk script detected via wish shebang
+package require Tk
+button .b -text "Click" -command {puts "clicked"}
+pack .b