Jim Brown's 1964 Cleveland Browns Championship ring has been PULLED OFF THE AUCTION BLOCK amid allegations the ring was stolen from the NFL legend back in the '60s ... TMZ Sports has learned.

Earlier this week, Brown sued Lelands Collectibles Inc. in the hopes of getting the ring back -- though he does NOT accuse the auction house of having anything to do with the original alleged heist.

Lelands is ADAMANT the ring was obtained legally after Brown gifted the item to a family member several decades ago.