Powerful 20-year-old attacking player Matthews-Lewis joins up with Spencer Day’s squad for the final few months of the season.
Millar has been with The Hatters from Under 14 level, right the way up to Paul Benson’s Development Squad.
Manager Spencer Day commented: “Millar is a young lad who has scored a lot of goals at Youth level.
“He’s been in training with us a couple of times now and again, we’re grateful and that’s the way I like it to be. With Premiership loans in particular, they have to run to the end of the season.
“He’s got a great attitude, scores goals, but he’s a young guy and he’ll have to bide his time and get into the team. He’s very keen and we’re delighted with the support Luton have given us.
“I think he’s got a great opportunity of putting himself in the shop window for his current employers moving forward for the rest of the season.”
Matthews-Lewis will wear shirt number 28.
View the updated Squad list here.