Watford have signed striker Obbi Oulare from Club Brugge, midfielder Adlene Guedioura from Crystal Palace, and forward Victor Ibarbo on loan from Cagliari.
Oulare, who has signed a five-year contract at Vicarage Road, is reported to have cost the Hornets £6million, while Guedioura returns to the club on a permanent three-year deal after two loan spells last season.
Ibarbo, meanwhile, arrives on a season-long loan, allowing Matej Vydra to join Reading on loan, also for the season.
Oulare, a Belgium Under-21 international, has scored nine goals in 39 starts for Club Brugge and recently made a substitute appearance against Manchester United in their Champions League play-off.
The 19-year-old came through the academy ranks at Lille in France before moving to Brugge in 2013.
Ibarbo, 25, scored one goal in 13 appearances on loan at Roma last season and has 14 caps for Colombia.
Algeria international Guedioura scored three goals in 17 appearances for Watford last season.