AirHint found the following cheapest return flights from Lisbon (LIS) to Keflavik (KEF) in August 2025 (see full year).

Return flights

25 Aug - 05 Sep	Ryanair
25 Aug - 30 Aug	Fly Play
29 Aug - 07 Sep	Fly Play
31 Aug - 07 Sep	Ryanair
22 Aug - 27 Aug	Ryanair
27 Aug - 05 Sep	Ryanair
16 Aug - 26 Aug	Ryanair
23 Aug - 30 Aug	Ryanair
30 Aug - 06 Sep	Ryanair
18 Aug - 23 Aug	Ryanair
22 Aug - 31 Aug	Ryanair
25 Aug - 04 Sep	Ryanair
15 Aug - 24 Aug	Ryanair
20 Aug - 27 Aug	Ryanair
31 Aug - 05 Sep	Ryanair
26 Aug - 05 Sep	Ryanair
11 Aug - 20 Aug	Ryanair
25 Aug - 05 Sep	Fly Play	direct
19 Aug - 26 Aug	Ryanair
31 Aug - 14 Sep	Vueling Airlines

Also check the deals for one-way flights from Lisbon to Keflavik in August.

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 Lisbon to Keflavik in August from $346

Return flights