Gillesphey's contract at Newcastle United had expired.
The 22-year-old centre-back has joined John Sheridan's side after penning a two-year deal with the club, following two loan spells at Brunton Park.
Carlisle United FC (@officialcufc) June 20, 2018
Gillesphey joined Carlisle on loan for the entire 2015-16 season, before rejoining the fourth-tier outfit during the second half of the 2016-17 season. He clocked up 63 appearances for Carlisle in total.
Now, he joins the club permanently following his Toon release, after Rafa Benitez failed to bring the versatile defender - who can also play at left-back - into the first team.
CARLISLE: Macauley Gillesphey set to return to full training next week following rehab programme pic.twitter.com/KLPAxQuVwP— BBC Cumbria Sport (@bbccumbriasport) November 28, 2015
The likes of Jamaal Lascelles, Florian Lejeune, Chancel Mbemba and Ciaran Clark have prevented Gillesphey from making a break into the first team of late.
After 54 appearances for Ben Dawson's Under-23 side, Gillesphey will be hoping he can reignite his career away from his boyhood club by helping Carlisle build on their tenth-placed finish last season and push for the play-offs.