LOS ANGELES/NEW YORK, Aug 24 (Reuters) - Marvel's hit space adventure "Guardians of the Galaxy" returned to win the domestic box office race in its fourth week of release, slaying the "Teenage Mutant Ninja Turtles" and ending the oversized reptiles' two-week reign at the top of the charts.

"Guardians," which also became the highest-grossing movie of the summer season, sold $17.6 million worth of tickets at U.S. and Canadian theaters for the three days starting on Friday.

"Turtles" took in $16.8 million in its third weekend to claim second place. "If I Stay," a new release about a 17-year-old in a coma and clinging to life, was third with $16.4 million.

Time Warner Inc's Warner Brothers distributed "If I Stay." "Teenage Mutant Ninja Turtles" was distributed by Viacom Inc's Paramount Pictures. Walt Disney Co distributed "Guardians of the Galaxy." (Reporting By Ronald Grover and Chris Michaud; Editing by Robin Pomeroy)