The Answer: The disputed champion is 2,953-foot Olo'upena Falls, on the northeastern coast of Molokai, Hawaii. But Bryan Swan, editor of worldwaterfalldatabase.com, says Olo'upena has never been officially measured, and in dry or windy weather, it can peter out mid-fall. Runners up include two more Aloha State falls (2,756-foot Pu'uka'oku Falls, also on Molokai, and 2,600-foot Waihilau Falls on the Big Island.) Stateside, Washington's 2,584-foot Colonial Falls wins–though it hasn't been officially measured either. And the iconic Yosemite Falls? The 2,425-foot gusher ranks sixth.
If you must see Olo'upena, take a 3-hour guided boat tour along Molokai's notoriously rugged north coast. It'll will get you within spray range–if the falls are flowing. hawaiiadventurehiking.com