Sunderland boss Mick McCarthy has completed the signing 24-year-old Nyron Nosworthy on a two-year deal.
Nosworthy played 199 games for Gillingham
The defender signed on a free transfer from Gillingham and will challenge Stephen Wright for a place next season.
"It feels very nice to be here and means a lot. I am quite calm at the moment - it has not sunk in yet that I am a Premier League player," he said.
"When I'm introduced to the rest of the lads next month, it will be different, but I am looking forward to it."
McCarthy said he was delighted to sign Nosworthy.
"He joins the club as an experienced defender despite his relatively young age," said McCarthy.
"I am sure he will provide Stephen Wright with strong competition for the right-back berth next season."
Nosworthy is the second summer signing for McCarthy, who bought Waterford striker Daryl Murphy for £100,000 last week.
Brixton-born Nosworthy joined the Gills as a schoolboy and played 199 games for the club, including 37 in the league last season.