AirHint found the following cheapest return flights from Riga (RIX) to Lisbon (LIS) in September 2025 (see full year).

Return flights

22 Sep - 26 Sep	Ryanair
22 Sep - 30 Sep	Ryanair
24 Sep - 30 Sep	Ryanair
20 Sep - 26 Sep	Ryanair
29 Sep - 04 Oct	Ryanair
16 Sep - 23 Sep	Ryanair
22 Sep - 27 Sep	Ryanair
09 Sep - 16 Sep	Ryanair
29 Sep - 03 Oct	Ryanair
20 Sep - 27 Sep	Ryanair
15 Sep - 23 Sep	Ryanair
08 Sep - 18 Sep	Ryanair
27 Sep - 06 Oct	Ryanair
27 Sep - 03 Oct	Ryanair

Also check the deals for one-way flights from Riga to Lisbon 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 Riga to Lisbon in September from $176

Return flights