J.J.K (Janus) Ooms (15 Augustus 1866, Amsterdam – 6 November 1924, Amsterdam) was a Dutch rower who was the first non-Briton to win the Diamond Challenge Sculls at Henley Royal Regatta (in 1892).
Ooms rowed for Neptune Rowing Club, Amsterdam, and was trained by Rudolf Meurer who also trained the Olympic champions François Brandt and Roelof Klein.
On his return to Amsterdam he was greeted by huge crowds and a fireworks display.After Ooms' victory, the Dutch Rowing Club awarded him a Golden Belt with the figure of a rower on it.
In 1921 he passed this on to the next Dutch rower to win the Diamond Challenge Sculls Frits Eijken.