The Portland Steel were a professional arena football team based in Portland, Oregon and members of the Arena Football League (AFL). The team started as the Portland Thunder, joining the AFL in 2014 as an expansion team along with the Los Angeles Kiss. The team played their home games at the Moda Center. They were known as the Thunder until the franchise went under league ownership in 2016 and became the Steel.

The Arena Football League (AFL) can refer to one of three successive professional indoor American football leagues in the United States. The first of these was founded in 1986, and played its first official games in the 1987 season, running for 22 consecutive seasons until going bankrupt following the 2008 season. The second league, consisting largely of teams from the first AFL and arenafootball2, purchased the first league's assets out of bankruptcy and resumed play in 2010 as a continuation of the first AFL; this second AFL ran for ten further seasons, before again going bankrupt following the 2019 season. The third and current AFL, which is not directly connected to the previous two iterations of the league but claiming their histories and trademarks, launched in 2024.