The World Open chess tournament is an annual open chess tournament usually held in Philadelphia. The inaugural event was held in New York in 1973 with 732 players, and was won by Walter Browne.
The tournament is divided into different sections, with typically 100–200 players in the top section. The 1986 edition had as many as 1507 participants, arguably a world record for a chess tournament. It is usually played in the first week of July, over Independence Day Weekend. All editions have been organized by the Continental Chess Association.