Björn Fallenius is a Swedish bridge player, for many years a resident of New York City. He and his wife Kathy Fallenius operate the Cavendish Bridge Club.
In world championship teams-of-four competition, Fallenius represented Sweden and won bronze medals in the 1987 and 1991 Bermuda Bowls and the 1988 World Team Olympiad. He also won bronze medals in the 1986 and 1998 Rosenblum Cups (on all-Swedish teams, although that quadrennial event is not nationally representative).
In pairs competition, Fallenius and Peter Fredin won the European Bridge League Open Pairs in 2009 and finished second in the 2010 World Open Pairs (silver medal). Fredin and Kathy Fallenius have played together in the World Mixed Pairs.