diff --git a/aider/commands.py b/aider/commands.py
index 6f6fb6acd..9cb7b4eb2 100644
--- a/aider/commands.py
+++ b/aider/commands.py
@@ -1088,7 +1088,7 @@ class Commands:
     def cmd_read_only(self, args):
         "Add files to the chat that are for reference, not to be edited"
         if not args.strip():
-            self.io.tool_error("Please provide filenames to read.")
+            self.io.tool_error("Please provide filenames or directories to read.")
             return
 
         filenames = parse_quoted_filenames(args)
@@ -1098,23 +1098,38 @@ class Commands:
             abs_path = self.coder.abs_root_path(expanded_path)
 
             if not os.path.exists(abs_path):
-                self.io.tool_error(f"File not found: {abs_path}")
+                self.io.tool_error(f"Path not found: {abs_path}")
                 continue
 
-            if not os.path.isfile(abs_path):
-                self.io.tool_error(f"Not a file: {abs_path}")
-                continue
-
-            if abs_path in self.coder.abs_fnames:
-                self.io.tool_error(f"{word} is already in the chat as an editable file")
-                continue
-
-            if abs_path in self.coder.abs_read_only_fnames:
-                self.io.tool_error(f"{word} is already in the chat as a read-only file")
-                continue
+            if os.path.isfile(abs_path):
+                self._add_read_only_file(abs_path, word)
+            elif os.path.isdir(abs_path):
+                self._add_read_only_directory(abs_path, word)
+            else:
+                self.io.tool_error(f"Not a file or directory: {abs_path}")
 
+    def _add_read_only_file(self, abs_path, original_name):
+        if abs_path in self.coder.abs_fnames:
+            self.io.tool_error(f"{original_name} is already in the chat as an editable file")
+        elif abs_path in self.coder.abs_read_only_fnames:
+            self.io.tool_error(f"{original_name} is already in the chat as a read-only file")
+        else:
             self.coder.abs_read_only_fnames.add(abs_path)
-            self.io.tool_output(f"Added {word} to read-only files.")
+            self.io.tool_output(f"Added {original_name} to read-only files.")
+
+    def _add_read_only_directory(self, abs_path, original_name):
+        added_files = 0
+        for root, _, files in os.walk(abs_path):
+            for file in files:
+                file_path = os.path.join(root, file)
+                if file_path not in self.coder.abs_fnames and file_path not in self.coder.abs_read_only_fnames:
+                    self.coder.abs_read_only_fnames.add(file_path)
+                    added_files += 1
+        
+        if added_files > 0:
+            self.io.tool_output(f"Added {added_files} files from directory {original_name} to read-only files.")
+        else:
+            self.io.tool_output(f"No new files added from directory {original_name}.")
 
     def cmd_map(self, args):
         "Print out the current repository map"