Celtics fans poured into Boston streets just seconds after Jayson Tatum and Jaylen Brown won the city an NBA title ... and they celebrated in chaotic fashion -- all while trashing Kyrie Irving in the process.
The impromptu block party began near TD Garden arena right after the C's mercifully ended the Dallas Mavericks' season by winning Game 5 of the NBA Finals, 106-88.
You can see thousands of green-clad fans flooded roadways -- jumping on top of police vehicles .