The zoo was named the Top Zoo in the World based on reviews submitted to TripAdvisor, which calls itself the world's largest travel website.
The Omaha zoo received the 2014 Travelers' Choice Award based on millions of reviews, TripAdvisor said. It beat out 275 zoos and aquariums in the U.S., Canada, Europe, India, Asia, the South Pacific and South America.
“Award winners were determined using an algorithm that took into account the quantity and quality of reviews for zoos and aquariums worldwide, gathering over a 12-month period," TripAdvisor said on its website.
The San Diego Zoo ranked second in the world and the St. Louis Zoo fourth. The top aquarium in the world was Monterey Bay Aquarium in California.
The Omaha zoo consistently draws more than a million visitors annually. Last year, it recorded 1,608,349 visits.
"Thirty-four percent of everybody who comes to the zoo comes from out-of-state," said CEO and Zoo Director Dennis Pate. "Some of them are from across the river (Iowa) but a lot of them are not."
Pate said the TripAdvisor award is a huge honor and a boost to the staff, who work hard to ensure visitors have a great experience.
"We're walking on clouds out here, frankly," Pate said. "It's neat that we had ... nothing to do with this list. It's totally from guest reviews."
All nine of the U.S. zoos ranked among the top 25 in the world are accredited by the Association of Zoos and Aquariums, which has the highest standards for zoos and aquariums. Pate said the TripAdvisor award raises the bar for Henry Doorly and those other zoos.
"It's a different lens that you look through now, knowing that the expectations are not Omaha, not just Nebraska and not the U.S.," he said. "It's a world standard that we are being held up to. ... We want to live up to that standard."
Henry Doorly spokeswoman Dawn Ream said the zoo has done a number of things in recent years to enhance visitor experiences, including adding the Skyfari aerial tram in 2009 and improving its front entrance to make it easier for people to get in.
The zoo also remodeled its aquarium and opened Stingray Beach, where visitors can interact with cownose rays and Southern stingrays. It also created Johnny Rosenblatt's Infield at the Zoo, a tribute to the iconic baseball stadium that was the zoo's longtime neighbor.
The zoo was founded by the city of Omaha in 1894 as Riverview Park.
In 1963, Margaret Hitchcock Doorly donated $750,000, with the stipulation that the zoo be named after her late husband, Henry Doorly, chairman of the World Publishing Co.
The Omaha Zoological Society was reorganized two years later to plan, construct, operate and maintain the zoo for the city as a nonprofit organization.