9:15 AM PT -- Cleveland Police tell TMZ Sports ... Lattimore was arrested during a traffic stop in which cops found a loaded handgun in his possession.
Cops say the gun was "later found to be entered as stolen out of the city of Euclid, Ohio."
Cops say there were 3 other people in the vehicle at the time of Lattimore's arrest ... all of whom were also arrested.
Two men were arrested for "having weapons while under disability." The driver was arrested for "improper handling of a firearm in a motor vehicle."
NFL star Marshon Lattimore -- a 3-time Pro Bowl cornerback -- was arrested in Cleveland around 10:30 p.m. on Thursday on suspicion of receiving stolen property.
The 24-year-old New Orleans Saints star was booked into the Cuyahoga County Jail early Friday morning ... where he posed for a mug shot while wearing a COVID mask.
Details surrounding the incident are unclear -- we're working on getting more info -- but Cleveland.com reports Lattimore was taken into custody by "Cleveland police’s gang investigators."
Lattimore -- the 11th overall pick in the 2017 NFL Draft -- was the league's Defensive Rookie of the Year in 2017 and has been a star player ever since ... making the Pro Bowl in 2017, 2019 and 2020.
Lattimore is about to enter the final year of his rookie contract -- which means he's expected to renegotiate for a TON of money ... but the arrest could seriously affect his contract situation.
Before his NFL career, Lattimore was a star at Ohio State -- where he was named 1st Team All-BIG 10 in 2016.
Lattimore grew up in the Cleveland area -- and was a star at Glenville High School where he was touted as one of the best defensive backs in the country.
Story developing ...
Originally Published-- 7:50 AM PT