Major League Rugby

In September 2016, with at least five amateur rugby union clubs across the United States discussing a possible professional league, Dean Howes, who had previously been an executive with Major League Soccer's Real Salt Lake and the St. Louis Blues of the National Hockey League, stepped in as senior strategic advisor for Rugby Utah in an attempt to provide a pathway for expanding professional rugby stateside.

By February 2017, a total of nine amateur rugby union organizations including the Austin Huns, Dallas Griffins, Glendale Raptors, Houston Strikers, Kansas City Blues, Minneapolis, New Orleans RFC, Rugby Utah and the Seattle Saracens, announced their intentions to form a professional league to begin play the following year.

On August 15, 2017, the Austin Huns announced that it would opt-out of MLR in favor of allowing a newly branded spinoff, the Austin Elite compete in the league. The Houston Strikers rebranded themselves as the Houston SaberCats. Whereas the elite players of New Orleans, Utah, and Seattle became the New Orleans Gold, Utah Warriors, and Seattle Seawolves respectively, interests in Minneapolis were replaced by the San Diego Legion. With Kansas City and Dallas still in planning stages, the league continued as seven members for its inaugural season.

On November 6, 2017, Major League Rugby and CBS Sports Network announced a multi-year television partnership which marked MLR's first major television deal for broadcast rights. It was the first time in American history that a new sporting league had a national television deal prior to launch.

The first regular-season game in Major League Rugby history was held on April 21, 2018, when the Houston SaberCats hosted the New Orleans Gold. The final was contested between the Seattle Seawolves and the Colorado Raptors, with the Seawolves winning 23–19 to become the inaugural champions.

In addition to Rugby United New York, the Toronto Arrows joined the league ahead of 2019 season as the first Canadian team in MLR. Three further American clubs began play in 2020: the New England Free Jacks, Old Glory DC, and Rugby ATL. With the opening of SaberCats Stadium as Houston's permanent stadium in April 2019, MLR gained its first stadium that was specifically built for league play.

Later in April, RUNY announced the signing of French international Mathieu Bastareaud on a loan deal from Toulon for the 2020 season. In October 2019, another major signing was made when it was announced that All Blacks international and multiple World Cup winner Ma'a Nonu would join the San Diego Legion for the 2020 season. The following December saw another World Cup winner sign with the league, namely South Africa prop Tendai Mtawarira with Old Glory DC.

On March 12, 2020, MLR initially suspended its 2020 season for 30 days due to the coronavirus pandemic, but then cancelled the remainder of the entire season on March 18, after five rounds had been played.

The LA Giltinis began competition in the 2021 season, followed by the Dallas Jackals, who entered in the 2022 season.

At the end of the 2022 regular season, MLR announced that the Giltinis and the Gilgronis—both owned by Adam Gilchrist, co-founder of F45 Training—were disqualified from the playoffs due to a violation of league rules, allegedly including salary cap issues. At the time of their disqualification, the Giltinis and Gilgronis were ranked first and second in the western conference. Gilchrist filed suit against the league and the two teams were expelled from the league in October following a failed attempt to sell both teams.

The Chicago Hounds began competition in the 2023 season. On February 8, 2023, Major League Rugby announced that the Miami Sharks would join the competition for the 2024 season. Following the 2023 season, Rugby ATL relocated from Atlanta to Los Angeles and rebranded as Rugby FC Los Angeles. In November 2023, the Toronto Arrows announced they would cease all operations following the death of founder Bill Webb and a failure to secure new investors. A week later, the New York Ironworkers announced they would also fold. On January 19, 2024, the league announced the creation of Anthem Rugby Carolina for the 2024 season. The team will serve as development team for US-eligible players, based upon the USA Hawks Under-23 men's development side. The team is financially supported by World Rugby, and unlike the other teams, its primary purpose will be to develop US-eligible players, in order to help qualify for the 2027 Rugby World Cup, and improve the USA Eagles as a competitive entity, before the USA-hosted 2031 Rugby World Cup.