Wilson directly replaces the departing Djilobodji
Wilson and McManaman have joined the club on permanent deals while Williams arrives on a season-long loan, with Wilson signing until the end of the season while McManaman signs a two-year contract.
The arrivals followed the loan departures of Papy Djilobodji and Wahbi Khazri to Ligue 1 sides Dijon FCO and Stade Rennais, and signal Simon Grayson's intention to acquire players with prior experience in English football.
Centre-back Wilson joins after seeing little first-team football for West Brom and Bournemouth in recent seasons, with his move to the latter from Stoke City only seeing him make three appearances.
The 30-year-old enjoyed his most fruitful spell during six seasons at Stoke, where he played 177 times including matches in the Premier League and Europa League as well as the 2011 FA Cup final against Manchester City.
Wilson has earned 25 caps for the Republic of Ireland since making his debut in February 2011 and has scored once, that goal coming in a 4-1 win against Faroe Islands in 2012.
Winger looking to make his mark on Wearside
McManaman failed to mark his mark at West Brom following a move from Wigan Athletic in January 2015, playing just 25 games and failing to score for The Baggies across two seasons.
He joined Championship outfit Sheffield Wednesday on loan for the second-half of last season and made 11 apperances for The Owls, recording two assists but failing to score. His last league goal came in Wigan's 3-1 defeat at Bolton Wanderers in November 2014.
The winger is an experienced Championship player and has played 78 games in the division, scoring 10 goals and recording six assists for Wigan, Blackpool and Sheffield Wednesday.
Fourth Championship loan spell for long-serving Eagles midfielder
The former Crystal Palace midfielder made his senior debut for The Eagles in 2011 and has gone on to make 93 appearances for the club, including 32 during their 2012/13 promotion season.
The 23-year-old spent last season on loan with Ipswich but made just eight appearances for The Tractor Boys after picking up a shoulder injury in December that kept him out for the rest of the season.
Williams has made 17 first-team appearances for Wales since making his debut in March 2013 and was part of the squad that reached the semi-final of Euro 2016.