diff --git a/docs/macros.md b/docs/macros.md
new file mode 100644
index 0000000..a251a41
--- /dev/null
+++ b/docs/macros.md
@@ -0,0 +1,27 @@
+---
+title: User Macros
+---
+
+Users may define macros for `zti`. When defined, user macros appear in the list of available commands for `zti`. User macros are created by placing Python files in the ZTI macros directory, which defaults to the path `~/.zti-mac`. This path may be overridden with the `ZTI_MACROS_DIR` environment variables.
+
+User macro file names must take the form `my_macro.py`, and must contain a function with the signature,
+
+```python
+    def do_my_macro(zti, arg):
+        ...
+```
+
+This function is invoked when the macro command is run from `zti`. It is passed the current `zti` instance as the first argument and any arguments to the command as the second argument.
+
+The macro file may optionally also contain a function with the signature,
+
+```python
+    def help_my_macro(zti):
+        ...
+```
+
+This function will be registered as the help command for the main macro command.
+
+See `examples/macros/logon.py` for an example of a user macro.
+
+User macros which conflict with existing ZTI commands are ignored.
\ No newline at end of file
diff --git a/examples/macros/logon.py b/examples/macros/logon.py
new file mode 100644
index 0000000..58122e4
--- /dev/null
+++ b/examples/macros/logon.py
@@ -0,0 +1,25 @@
+from tnz import ati
+
+def do_logon(zti, arg):
+    logon_setup()
+    ati.wait(lambda: ati.scrhas("Enter:  "))
+    ati.send("app1 userid[enter]")
+    ati.wait(lambda: ati.scrhas("Password  ===> "))
+    ati.send("password[enter]")
+
+    # maybe look for a status message
+    ati.wait(lambda: ati.scrhas("ICH70001I"))
+
+    # do something useful
+    ati.wait(lambda: ati.scrhas("***"))
+    ati.send("[enter]")
+    ati.wait(lambda: ati.scrhas("READY"))
+
+def logon_setup():
+    ati.set("TRACE", "ALL")
+    ati.set("LOGDEST", "example.log")
+
+    ati.set("ONERROR", "1")
+    ati.set("DISPLAY", "HOST")
+    ati.set("SESSION_HOST", "mvs1")
+    ati.set("SESSION", "A")
diff --git a/tnz/zti.py b/tnz/zti.py
index 46d4141..98989a1 100644
--- a/tnz/zti.py
+++ b/tnz/zti.py
@@ -57,6 +57,7 @@
 import cmd
 import logging
 import os
+import pathlib
 import platform
 import signal
 import sys
@@ -173,6 +174,8 @@ def __init__(self, stdin=None, stdout=None):
 
         self.__install_plugins()
 
+        self.__register_macros()
+
     # Methods
 
     def atexit(self):
@@ -2704,6 +2707,73 @@ def __refresh(self):
 
         self.stdscr.refresh(_win_callback=self.__set_event_fn())
 
+    def __register_macros(self):
+        import importlib.util
+        import sys
+        import types
+
+        macros_dir = os.getenv("ZTI_MACROS_DIR")
+        if macros_dir is None:
+            macros_dir = os.path.expanduser("~/.zti-mac")
+
+        if not os.path.isdir(macros_dir):
+            _logger.error(f"{macros_dir} is not a directory")
+            return
+
+        for macro_file in os.listdir(macros_dir):
+            macro_file_path = pathlib.PurePath(macro_file)
+
+            if macro_file_path.suffix != ".py":
+                continue
+
+            macro_name = macro_file_path.stem
+
+            # Ignore macros with uppercase letters or
+            # spaces
+            if ' ' in macro_name or not macro_name.islower():
+                continue
+
+            # Ignore macros which already exist
+            if f"do_{macro_name}" in self.get_names():
+                _logger.warning(f"Function with name do_{macro_name}"
+                                " already exists, macro registration"
+                                " failed")
+                continue
+
+            macro_path = os.path.join(macros_dir, macro_file)
+
+            # Import the user macro as a module
+            macro_spec = importlib.util.spec_from_file_location(
+                f"module.{macro_name}", macro_path)
+            macro_module = importlib.util.module_from_spec(macro_spec)
+            sys.modules[f"module.{macro_name}"] = macro_module
+            macro_spec.loader.exec_module(macro_module)
+
+            # Find the function
+            if hasattr(macro_module, f"do_{macro_name}"):
+                def do_macro(zti, arg):
+                    self.__bg_wait_end()
+                    macro_func = getattr(macro_module,
+                                         f"do_{macro_name}")
+                    macro_func(zti, arg)
+
+                # Create a new bound method for the `Zti` class for this
+                # function
+                setattr(Zti, f"do_{macro_name}",
+                        types.MethodType(
+                            do_macro,
+                            self))
+
+                # Check if a corresponding help function exists
+                if hasattr(macro_module, f"help_{macro_name}"):
+                    # Create a new bound method for the `Zti` class
+                    # for this function
+                    setattr(Zti, f"help_{macro_name}",
+                            types.MethodType(
+                                getattr(macro_module,
+                                        f"help_{macro_name}"),
+                                self))
+
     def __scale_size(self, maxrow, maxcol):
         arows, acols = self.autosize
         aspect1 = arows / acols