Watford will play Premier League football next season after their 2-0 win at Brighton and Hove Albion was followed by Middlesbrough and Norwich City failing to secure victory on Saturday.
Promotion seals a return to the top flight after eight seasons in the second tier for Watford, who were relegated at the end of the 2006-07 campaign.
Goals from Troy Deeney – his 21st of the season – and Matej Vydra secured victory for Slavisa Jokanovic’s side in the early kick-off at the Amex Stadium.
That result meant Boro would have to avoid defeat or Norwich would have to win to prevent Watford from going up, and neither side was able to deny the league leaders.
Third-placed Boro went down 4-3 in a thriller at Fulham, Ross McCormack completing his hat-trick in the fourth minute of stoppage time to effectively seal Watford’s elevation.
Norwich, meanwhile, saw Lewis Grabban sent off in the first half of their 1-1 draw at relegation-threatened Rotherham United, for whom Jordan Bowery’s late goal cancelled out Gary Hooper’s opener.
Saturday’s results mean Bournemouth can all but guarantee promotion with a home win over Bolton Wanderers on Monday.
Eddie Howe’s men are level on points with Middlesbrough but boast a vastly superior goal difference ahead of their penultimate match.