Niagara Glen Nature Reserve, Protected area in Ontario, Canada.

Niagara Glen Nature Reserve is a protected area in Ontario featuring walking trails through a mature deciduous forest next to the Niagara River Gorge and Whirlpool. The paths wind along cliff faces and reveal natural formations carved by water and glacial action over thousands of years.

The reserve was established to protect the rare Carolinian Forest ecosystem that now survives in only small pockets across southern Ontario. The gorge itself was carved by glaciers during the last Ice Age and subsequently shaped by flowing water over thousands of years.

The reserve protects one of the best-preserved remaining stands of Southern Ontario's original Carolinian forest, a zone where species typical of more southerly regions grow. Visitors walking the trails pass through this woodland on the Canadian side of the Niagara Gorge, near the whirlpool.

Hikers are advised not to leave the marked trails, as entering the Niagara River from the trail is dangerous and has led to emergency rescues. The river's rapids are life-threatening, and rescues involve the Niagara Parks Police, fire departments, emergency medical services, and the Canadian and United States Coast Guards.

The glen holds a dense concentration of limestone boulders, making it one of Southern Ontario's main bouldering areas. In 2012 the Niagara Parks Commission and the Ontario Alliance of Climbers jointly created a bouldering permit system, after restrictions prompted debate over whether climbing should continue.