Freestyle queen Katie Ledecky made sure of her third swimming gold medal of the Rio Olympics, and fourth of her career, after anchoring the U.S. women to victory in the 4x200 meters freestyle relay on Wednesday.

Australia, who led until Ledecky hit the water, took silver and Canada the bronze.

The U.S. were the defending champions but only Allison Schmitt, who swam the leadoff leg in Rio, was in the race lineup from that London 2012 golden quartet that also beat Australia into second place.

Leah Smith and Maya DiRado swam second and third respectively before Ledecky, who won the 400 freestyle on Sunday and 200 free on Tuesday, brought home the gold with a typically powerful swim from behind.

China led at the start before Australia, with Emma McKeon swimming the second leg, handed over in the lead to Bronte Barratt.

With DiRado closing in on Barratt but still behind, Ledecky had work to do and she went about it with a vengeance to take the lead with just over 100m to go and then powering home in seven minutes, 43.03 seconds.

Tamsin Cook touched out for Australia in 7:44.57 and Canada's anchor Penny Oleksiak finished close behind in 7:45.39 with China fourth.