The 2009 Taconic State Parkway crash was a traffic collision that occurred shortly after 1:30 p.m. on Sunday, July 26, 2009, on the Taconic State Parkway in the town of Mount Pleasant, near Briarcliff Manor, New York. Eight people were killed when a minivan driven by 36-year-old Diane Schuler, after traveling 1.7 miles in the wrong direction on the parkway, collided head-on with an oncoming SUV. The deaths included Schuler, her daughter and three nieces, and the three passengers in the SUV. The crash was the worst fatal motor vehicle accident in Westchester County, New York,since a July 22, 1934 bus accident in Ossining claimed 20 lives.

The ensuing investigation into the crash's cause received nationwide attention. Toxicology tests conducted by the medical examiner revealed that Schuler was heavily intoxicated with both alcohol and marijuana at the time of the crash. Schuler's husband, Daniel, has consistently denied that she used drugs or alcohol excessively, and has made multiple media appearances to defend his wife and call for further investigation into other possible medical causes for her erratic driving. An independent investigator hired by the Schuler family obtained DNA testing and toxicology testing of Diane Schuler's samples, which confirmed the results of the original testing.