Three judges awarded the verdict in favour of Russia's Vladimir Nikitin in the quarter-final of the men's bantamweight 56kg, despite Conlan's protestations.
The 24-year-old told BBC Sport: "I came for gold and I've been cheated. I'll not do another Olympics. I would advise anybody not to compete for the AIBA (Amateur International Boxing Association).
"At the end of the first round, it had been so easy, so comfortable, I wasn't even out of breath. I said 'I'll win this easy'. But I was told I was down. I had to go to war.
"I fought him at his own game. I pulled back that second round then I outfought him in the last round. I've been robbed of my Olympic dream."
Conlan's contentious defeat comes after a hugely controversial decision in Monday's heavyweight boxing final when another Russian, Evgeny Tishchenko, was given the verdict over Kazakhstan's Vassiliy Levit.