A trophyless campaign, which saw Jose Mourinho replaced by Ole Gunnar Solskjaer at the helm, ended with a 2-0 home defeat to already-relegated Cardiff on Sunday.
The Red Devils finished sixth on 66 points, 32 points behind champions Manchester City and the same amount in front of 18th-placed Cardiff.
The gap between United and City means it is the furthest the club have been from the top since regaining their top-flight status in 1975.
And the 32-point gap eclipses the 31-point margin that Liverpool had over 13th-placed United when they last won the league in 1990.
United’s hopes of finishing in the top four were ruined with a run of just two wins from their final nine games.
It has been a dire end to the season for Solskjaer, who had won 14 of his 17 games in all competitions in temporary charge before being appointed on a full-time basis in March.
The Norwegian is set to be busy in the summer transfer window with Ander Herrera and Antonio Valencia on their way out, while Matteo Darmian and Juan Mata are expected to follow them out the door.
And after ruling out a title challenge next term, Solskjaer is targeting a top four push.
He said: “We have been poor. We’ve more or less hit a brick wall towards the end of the season so that’s very disappointing.
“We were in with a shout (of the top four) but the last two games, of course, we’ve let ourselves down performance-wise.
“We should have won against two relegated teams (United drew 1-1 at Huddersfield last week) but that’s another reality check for everyone.
“This league is a tough one, no matter who you play, and it’s a long season and towards the end we’ve performed under par.