Karl Ruben
Karl Ruben was a Danish chess master.
He won a match against Johannes Pedersen at Aalborg 1927, tied for 2nd-3rd in Danish Championship at Vordingborg 1927, shared 2nd at Copenhagen 1927,
tied for 5-6th at Copenhagen 1928, tied for 7-9th at Svendborg 1930, and won a simultan game against Alexander Alekhine at Copenhagen 1930.
Ruben played four times for Denmark in Chess Olympiads in 1927, 1928, 1930, 1931, and won team silver medal at London 1927.