Cuthbert, 27, has put pen to paper on a two-year deal after seeing his contract with the O’s expire.
Hatters boss John Still thinks he has gained an experienced centre-half that will help the club mount a serious challenge for promotion next season.
“When you set your targets you don’t always get them but Scott was the one we wanted. We stuck at it and we’ve got him,” said Still.
“He’s impressed us as we didn’t have to push him towards us, he wanted to come here. Scott’s dropped a level but he thinks he can get back up to League One and beyond in his time with us.
“He’s a warrior, he’s got leadership qualities; he’s a good talker and a good organiser. When you sign an experienced player like this you want them to put it to good use and I think Scott will.
“He was the top man at Orient and I’m delighted with this capture. We felt it was important to bring in a player that will come in and make all our centre-backs look at each other and ask ‘who is going to play?’ And that’s what we want.”