Clippers forward Amir Coffey was arrested in L.A. on Sunday morning ... after cops say they found a loaded gun in his ride during a routine traffic stop.
Law enforcement tells TMZ Sports ... officers pulled over a car that Coffey was a passenger in at around 2:30 a.m. in Hollywood -- after they say they saw it speeding.
When cops approached the vehicle, they said it smelled like marijuana -- so they searched it, and found a loaded gun.
Cops say Coffey admitted it was his -- and he was then arrested for misdemeanor possession of a firearm.