The UFC star has finally returned to Ireland after that violent bus attack in Brooklyn ... but instead of soaking up the spotlight (as usual), he shot photogs the 1-finger salute.

As we previously reported ... after McGregor was released from jail on April 6, he flew to the Bahamas for a little R&R with his girlfriend, Dee Devlin, and his kid, Conor McGregor Jr.

But now, Conor has returned back to Ireland ... and he doesn't look too happy.

Maybe it's because he's due back in court in Brooklyn in June ... or because some of his fellow countrymen feel he brought great shame on his country.