Republic of Ireland international John Egan has signed a four-year deal with Sheffield United from fellow Championship side Brentford United.
The 25-year-old Cork native is the club's new record signing.
Egan, who has two international caps, made 81 league appearances for Gillingham as well as 67 for Brentford over the last two seasons.
"It's been a long time since I was first here, but it fantastic to be back at such a big club," a delighted Egan told the Sheffield United website after putting pen to paper.
"When a manager, especially one of Chris's stature wants to sign you so much, as a player it makes you feel really wanted.
"As soon as I heard of United's interest and having spoken to the manager I was eager to get the deal over the line.
"I've two fantastic years at Brentford, I can't speak about them highly enough and we had a very good team there," added Egan, who is the son of the late, great Kerry footballer John Egan.
"But now I really want to kick on at Sheffield United. I love a team in red and white stripes and I just can't wait to get going again at Bramall Lane.
"I've been back with Gillingham and last season with Brentford, the place was rocking on the opening day of the season.
"The fans have always been unbelievable here and I can't wait to walk out as a Blade now."