Michael Phelps earned a trip to his fifth Olympic Games Wednesday at the U.S. Olympic trials in the 200 metre butterfly, almost 16 years after qualifying for his first Olympics in the same event.

With a time of one minute and 54.48 seconds, Phelps is the first American swimmer to qualify for five Games.

Wednesday's swim was not the near-perfect swim we have come to expect from the 22-time Olympic medallist and current world-record holder in the event as Phelps didn't hit all three turns with arms extended and appeared to tighten up in the final 15 meters.

"That was probably harder than any swim I've had in my life," Phelps told after the race.

"It was my last 200 fly on American soil, my last race as a 30-year-old and I was going for my fifth Olympics.

"It looked like Boomer [his baby son] was awake for the race, which was good.

"Not as fast as I would like to have been, but at this point it's all about just getting on the team."

Phelps is in a great position to cut additional time at Rio as he fully tapers in what is expected to be one of the greatest races of the Games alongside Hungary's Laszlo Cseh, who owns the fastest time in the world since 2015 (1:52.91), and South Africa's Chad le Closs (1:53.68).

Tom Shields will join Phelps in the 200 butterfly in Rio after finishing second in a time of 1:55.81 — his first trip to the Olympics.

Phelps is expected to defend his Olympic trials title in the 100 butterfly and 200 individual medley as the eight-day meet continues.