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.

During the 1990s, the suitability of the Mariners' original stadium—the Kingdome—as an MLB facility came under question, and the team's ownership group threatened to relocate the team. In September 1995, King County voters defeated a ballot measure to secure public funding for a new baseball stadium. Shortly thereafter, the Mariners' first appearance in the MLB postseason and their victory in the 1995 American League Division Series (ALDS) revived public desire to keep the team in Seattle. As a result, the Washington State Legislature approved an alternate means of funding for the stadium with public money. The site, just south of the Kingdome, was selected in September 1996 and construction began in March 1997. The bonds issued to finance Safeco Field were retired on October 1, 2011, five years earlier than anticipated.

T-Mobile Park is also used for amateur baseball events, including the Washington Interscholastic Activities Association high school state championships and one Washington Huskies game per season. Major non-baseball events that have been held at T-Mobile Park include the 2001 Seattle Bowl and WrestleMania XIX in 2003, which attracted the stadium's record attendance of 54,097.

The stadium was originally named Safeco Field under a 20-year naming-rights deal with Seattle-based Safeco Insurance. T-Mobile acquired the naming rights on December 19, 2018, and the name change took effect on January 1, 2019.