Rainbow Falls is the name of several waterfalls:

New Zealand:

• Rainbow Falls (Waianiwaniwa), at Kerikeri
• Āniwaniwa Falls (Rainbow Falls) near Lake Waikaremoana

Canada:

• Rainbow Falls, British Columbia

United States:

• Rainbow Falls, Adirondack State Park, New York
• Rainbow Falls (California), Devils Postpile National Monument, California
• Rainbow Falls (Chattooga River), Cashiers, North Carolina
• Rainbow Falls (Chelan County), Stehekin, Washington
• Rainbow Falls (Hawaii), Hilo, Hawaii
• Rainbow Falls (Horsepasture River), Transylvania County, North Carolina
• Rainbow Falls (Manitou Springs, Colorado)
• Rainbow Falls (Michigan), Black River, Michigan
• Rainbow Falls (Missouri River), Great Falls, Montana
• Rainbow Falls (Montana), Glacier National Park
• Rainbow Falls (Rutherford County), Rutherford County, North Carolina
• Rainbow Falls State Park, Lewis County, Washington

Computing Systems:

• SPARC T3, a microprocessor also known as "Rainbow Falls"

Other:

• Rainbow Falls Trail
• Rainbow Falls, an episode of the fourth season of My Little Pony: Friendship Is Magic