T-Mobile Park is a retractable roof stadium in Seattle, Washington, United States. It is the ballpark of Major League Baseball's Seattle Mariners and has a seating capacity of 47,929. It is in Seattle's SoDo neighborhood, near the western terminus of Interstate 90. It is owned and operated by the Washington State Major League Baseball Stadium Public Facilities District. The first game at the stadium was played on July 15, 1999.

A retractable roof is a roof system designed to roll back the roof of a structure so that the interior of the facility is open to the outdoors. Retractable roofs are sometimes referred to as operable roofs or retractable skylights. The term operable skylight, while quite similar, refers to a skylight that opens on a hinge, rather than on a track.