A young man is fighting for life after a brawl in Melbourne's CBD at the weekend.

Police were called to the fight, which erupted at Batman Park in the early hours of Sunday morning.

It's unclear what initiated the clash, however, police believe there was some sort of altercation between two groups that escalated into a brawl just after 4am.

A brawl at Batman Park in Melbourne's CBD has left a 21-year-old in a critical condition. Credit:Nine News

A 21-year-old man was rushed to The Alfred hospital by paramedics with serious upper body injuries.