AirHint found the following cheapest return flights from Southampton (SOU) to Belfast (BFS) in September 2025 (see full year).

Return flights

26 Sep - 06 Oct	easyJet	direct
25 Sep - 26 Sep	easyJet	direct
26 Sep - 27 Sep	easyJet	direct
25 Sep - 27 Sep	easyJet	direct
26 Sep - 29 Sep	easyJet	direct
26 Sep - 28 Sep	easyJet	direct
25 Sep - 30 Sep	easyJet
24 Sep - 26 Sep	Aer Lingus	direct
20 Sep - 23 Sep	Aer Lingus	direct
17 Sep - 23 Sep	Aer Lingus	direct
16 Sep - 23 Sep	Aer Lingus	direct
23 Sep - 07 Oct	Aer Lingus	direct
27 Sep - 05 Oct	easyJet	direct
28 Sep - 05 Oct	Aer Lingus	direct
27 Sep - 06 Oct	Aer Lingus	direct

Also check the deals for one-way flights from Southampton to Belfast in September.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Southampton to Belfast in September from $66

Return flights