Odell Beckham came through with an amazing gesture for a man fighting cancer ... by sending a personal message of encouragement during his challenging time.
TMZ Sports is told ... 43-year-old Dominic Tafuri is a former MMA fighter and current officer with the Essex County Department of Corrections in NJ.
Dominic also worked for Odell's go-to guy for bling, Gabriel the Jeweler ... delivering pieces to some of the biggest athletes around the world -- from Aaron Donald to Prince Boateng to Ederson.
Tafuri recently found out he had Stage 4 lymphoma after undergoing a routine ACL surgery ... and is now battling the disease head-on.
We're told Tafuri is like a brother to Gabriel, so the jeweler hit up OBJ and asked him to improve Dominic's spirits ... and the Rams star delivered!!
"Dominic, what's going on, man? OBJ here, bro," Odell said in the video. "Just wanted to reach out to you, send some love your way."
"Just stay encouraged, man," he added. "Stay prayed up, man. Just know I'm praying for you, and just wanted to send some love, bro. Stay up."
FYI -- there's a GoFundMe set up to help Dominic and his family during this time ... with a goal of raising $100k.
Awesome move by OBJ ... and keep fighting, Dominic!!