Hatters have made former Derby County defender Mark O’Brien their 10th signing of the summer.
The 22-year-old was recently released by the Rams, after spending time on loan at Scottish Premier League side Motherwell last season, making 21 appearances.
O’Brien, who has played for Ireland at U19 level, and represented Derby in the Championship, is currently on Town’s pre-season training camp in Portugal and has penned a two year deal.
He featured as a trialist in both halves against Farense during Tuesday’s warm-up match and can also operate at full-back and in central midfield.
On signing for the Hatters, O’Brien tweeted: “I am delighted to say I have signed for Luton Town, I can’t wait for the new season to begin.”