AirHint found the following cheapest return flights from Porto (OPO) to Singapore (SIN) in September 2025 (see full year).

Return flights

25 Sep - 07 Oct	SWISS
24 Sep - 08 Oct	SWISS
23 Sep - 08 Oct	SWISS
25 Sep - 08 Oct	SWISS
20 Sep - 08 Oct	SWISS
25 Sep - 19 Oct	SWISS
26 Sep - 19 Oct	Ryanair
16 Sep - 01 Oct	SWISS
09 Sep - 25 Sep	Ryanair
19 Sep - 21 Sep	Ryanair
01 Sep - 08 Sep	Ryanair
01 Sep - 10 Sep	easyJet
02 Sep - 11 Sep	easyJet
06 Sep - 13 Sep	Vueling Airlines
01 Sep - 15 Sep	easyJet
01 Sep - 11 Sep	Turkish Airlines
17 Sep - 24 Sep	TAP

Also check the deals for one-way flights from Porto to Singapore 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 Porto to Singapore in September from $701

Return flights