diff --git a/core/modules/new_widgets/macrodef.js b/core/modules/new_widgets/macrodef.js
new file mode 100644
index 000000000..a386fe4ab
--- /dev/null
+++ b/core/modules/new_widgets/macrodef.js
@@ -0,0 +1,55 @@
+/*\
+title: $:/core/modules/new_widgets/macrodef.js
+type: application/javascript
+module-type: new_widget
+
+Macro definition widget
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+var Widget = require("$:/core/modules/new_widgets/widget.js").widget;
+
+var MacroDefWidget = function(parseTreeNode,options) {
+	this.initialise(parseTreeNode,options);
+};
+
+/*
+Inherit from the base widget class
+*/
+MacroDefWidget.prototype = new Widget();
+
+/*
+Render this widget into the DOM
+*/
+MacroDefWidget.prototype.render = function(parent,nextSibling) {
+	this.parentDomNode = parent;
+	this.computeAttributes();
+	this.execute();
+	this.renderChildren(parent,nextSibling);
+};
+
+/*
+Compute the internal state of the widget
+*/
+MacroDefWidget.prototype.execute = function() {
+	// Set macro definition
+	this.setVariable(this.parseTreeNode.name,this.parseTreeNode.text,this.parseTreeNode.params);
+	// Construct the child widgets
+	this.makeChildWidgets();
+};
+
+/*
+Selectively refreshes the widget if needed. Returns true if the widget or any of its children needed re-rendering
+*/
+MacroDefWidget.prototype.refresh = function(changedTiddlers) {
+	return this.refreshChildren(changedTiddlers);
+};
+
+exports.macrodef = MacroDefWidget;
+
+})();
diff --git a/core/modules/wiki.js b/core/modules/wiki.js
index 50583206a..479cfbf12 100755
--- a/core/modules/wiki.js
+++ b/core/modules/wiki.js
@@ -629,19 +629,35 @@ exports.parseTiddler = function(title,options) {
 
 // We need to tweak parse trees generated by the existing parser because of the change from {type:"element",tag:"$tiddler",...} to {type:"tiddler",...}
 var tweakParseTreeNode = function(node) {
-		if(node.type === "element" && node.tag.charAt(0) === "$") {
-			node.type = node.tag.substr(1);
-		}
-		tweakParseTreeNodes(node.children);
-	},
-	tweakParseTreeNodes = function(nodeList) {
-		$tw.utils.each(nodeList,tweakParseTreeNode);
-	};
+	if(node.type === "element" && node.tag.charAt(0) === "$") {
+		node.type = node.tag.substr(1);
+	}
+	tweakParseTreeNodes(node.children);
+};
+
+var tweakParseTreeNodes = function(nodeList) {
+	$tw.utils.each(nodeList,tweakParseTreeNode);
+};
+
+var tweakMacroDefinition = function(nodeList) {
+	if(nodeList && nodeList[0] && nodeList[0].type === "macrodef") {
+		nodeList[0].children = nodeList.slice(1);
+		nodeList.splice(1,nodeList.length-1);
+		tweakMacroDefinition(nodeList.children);
+	}
+};
+
+var tweakParser = function(parser) {
+	// Move any macro definitions to contain the body tree
+	tweakMacroDefinition(parser.tree);
+	// Tweak widgets
+	tweakParseTreeNodes(parser.tree);
+};
 
 exports.new_parseText = function(type,text,options) {
 	var parser = this.parseText(type,text,options);
 	if(parser) {
-		tweakParseTreeNodes(parser.tree)
+		tweakParser(parser)
 	};
 	return parser;
 };
@@ -649,7 +665,7 @@ exports.new_parseText = function(type,text,options) {
 exports.new_parseTiddler = function(title,options) {
 	var parser = this.parseTiddler(title,options);
 	if(parser) {
-		tweakParseTreeNodes(parser.tree)
+		tweakParser(parser)
 	};
 	return parser;
 };