Flamengo have won the Brazilian championship without kicking a ball, just 24 hours after their dramatic Copa Libertadores victory.
Gremio scored a 94th-minute winner against Palmeiras to give Flamengo an unassailable 13-point lead in Serie A with four games remaining.
It is the Rio club's seventh league title and their first since 2009.
On Saturday, they beat River Plate to be crowned South American champions for the first time since 1981.
Gabriel Barbosa scored twice in a dramatic final five minutes in Lima as Flamengo came from a goal down to win 2-1 in the Copa Libertadores final.
It is the first time that a Brazilian team have won both the league and the Libertadores in the same year since Pele's Santos achieved the same feat in 1963.
Flamengo were crowned Brazilian champions following a homecoming parade in Rio.
Fighting broke out towards the end of the celebrations, with stones and bottles thrown at police who responded with tear gas.