Ten people are killed in a mass shooting in Boulder, Colorado.

On March 22, 2021, a mass shooting occurred at a King Soopers supermarket in Boulder, Colorado, United States. Ten people were killed, including a local on-duty police officer. The shooter, 21-year-old Ahmad Al Aliwi Al-Issa, was arrested after being shot in the right leg. He was temporarily hospitalized before being moved to the county jail. After undergoing mental evaluations during the legal proceedings, Al-Issa was found mentally incompetent to stand trial in December 2021 and in April 2022. On August 23, 2023, prosecutors announced that Al-Issa was mentally competent to stand trial; a judge ruled as such on October 6 of that same year. On September 23, 2024, Al-Issa was found guilty in the shooting and sentenced to life in prison without the possibility of parole.

Boulder is a home rule city in Boulder County, Colorado, United States, and its county seat. With a population of 108,250 at the 2020 census, it is the most populous city in the county and the 12th-most populous city in Colorado. It is the principal city of the Boulder metropolitan statistical area, which had 330,758 residents in 2020 and is part of the Front Range Urban Corridor.

March 22 is the 81st day of the year in the Gregorian calendar; 284 days remain until the end of the year.