Georgian Bay is about 320 kilometers long by 80 kilometers wide. It covers over 15,000 square kilometers, making it almost as large as Lake Ontario. Eastern Georgian Bay is part of the southern edge of the Canadian Shield, granite bedrock exposed by the glaciers at the end of the last ice age, about 11,000 years ago. The granite rock formations and windswept Eastern White Pine are characteristic of the islands and much of the shoreline of the bay. The rugged beauty of the area inspired landscapes by artists of the Group of Seven. The western part of the bay, from Collingwood north, and including Manitoulin Island, Drummond, Cockburn and St. Josephs Island, borders the Niagara Escarpment.

Georgian Bay was first charted in 1815 by Captain William Fitzwilliam Owen, who called it Lake Manitoulin. Captain Henry Bayfield, who made much more detailed charts of the bay, renamed it in 1822 after King George IV; his charts are the basis of those in use today.

There are tens of thousands of islands in Georgian Bay. Most of these islands are along the east side of the bay and are collectively known as the "Thirty Thousand Islands," including the larger Parry Island. Manitoulin Island, lying along the northern side of the bay, is the world's largest island in a freshwater lake. The Trent-Severn Waterway connects Georgian Bay to Lake Ontario, running from Port Severn in the south-eastern corner of Georgian Bay through Lake Simcoe into Lake Ontario near Trenton. Further north, Lake Nipissing drains into it through the French River. In October 2004, the Georgian Bay Littoral was declared a Biosphere Reserve by UNESCO.

Just a few of the amazing things to in and around Georgian Bay: