John Blankenstein (12 February 1949 in De Bilt – 25 August 2006 in The Hague) was a Dutch football referee and gay rights activist.

In 1994, Blankenstein was selected to referee the 1994 UEFA Champions League Final between AC Milan and FC Barcelona, only to be replaced by Englishman Philip Don a few days before the match.

The contents of the official decision were never made public, but it was said that it was because Johan Cruijff and Ronald Koeman, both FC Barcelona players, were from the Netherlands.

For breaking with the taboo on the subject of homosexuality in football, the Dutch LGBT advocacy organization COC Nederland awarded him the Bob Angelo medal in 2003.

To continue his work for acceptance of and equal rights for homosexual people in sports, the John Blankenstein Foundation was founded on 18 December 2008.