Mick Harford's side were unable to preserve their League status
Luton's relegation from the Football League was confirmed after they were held to a 0-0 draw by Chesterfield.
The result, coupled with Grimsby's win at Notts County, means that the Hatters cannot get out of the bottom two.
Luton made a brave attempt to remain in League Two, but a 30-point deduction for financial infringements proved too much to overcome.
Luton have been in the Football League for 89 years and won the League Cup in 1988, beating Arsenal in the final.
They won at Wembley only eight days ago, when Claude Gnakpa scored an extra-time winner to secure victory in the Johnstone's Paint Trophy in a fine match.
Glory at Wembley, with a record Hatters 40,000 fans in attendance, was a welcome reward for Luton after a season in which they were all but doomed to the drop before a ball was kicked.
Luton boss Mick Harford has guided his side to 13 victories so far this season, with 15 draws and 14 defeats - a record which would have left the club comfortably in mid-table, if the points deduction had not been in place.
But with four games left to play, the Hatters will have to start preparing for life outside the Football League.
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