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

Return flights

31 Aug - 07 Sep	easyJet
30 Aug - 07 Sep	Ryanair
25 Aug - 01 Sep	Fly Play	direct
25 Aug - 30 Aug	Fly Play
28 Aug - 31 Aug	TAP
21 Aug - 27 Aug	TAP
30 Aug - 06 Sep	TAP
12 Aug - 19 Aug	Ryanair
15 Aug - 18 Aug	Fly Play	direct
21 Aug - 26 Aug	TAP
31 Aug - 05 Sep	Air Europa
11 Aug - 18 Aug	Ryanair
21 Aug - 29 Aug	TAP
06 Aug - 20 Aug	TAP
21 Aug - 25 Aug	TAP
31 Aug - 07 Sep	Icelandair	direct

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 289€

Return flights