Roberto De Zerbi told Brighton supporters to get their passports ready but warned the club must continue improving ahead of their maiden European campaign next season.
Evan Ferguson netted twice in the first half of Albion's 3-1 victory over Southampton in front of a sold-out Amex Stadium, where Pascal Gross restored the two-goal advantage following Mohamed Elyounoussi's header for the relegated Saints.
The three points assured De Zerbi's side would not finish lower than seventh, in the Europa Conference League spot, though a sixth-place finish and a Europa League berth are all but mathematically guaranteed.
'Today is difficult for me because with my English I can't explain my emotion,' said the Italian manger, who succeeded Graham Potter in September.