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

Return flights

15 Dec - 17 Dec	easyJet
07 Dec - 14 Dec	Jet2
10 Dec - 17 Dec	easyJet
11 Dec - 18 Dec	easyJet
15 Dec - 21 Dec	Wizz Air Malta
15 Dec - 20 Dec	Wizz Air Malta
29 Dec - 05 Jan	easyJet
21 Dec - 07 Jan	Scandinavian Airlines
18 Dec - 04 Jan	easyJet
28 Dec - 31 Dec	easyJet
07 Dec - 14 Dec	Icelandair	direct
18 Dec - 03 Jan	easyJet
11 Dec - 18 Dec	Icelandair	direct
21 Dec - 04 Jan	Scandinavian Airlines
21 Dec - 29 Dec	Scandinavian Airlines

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

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 Keflavik to Lisbon in December from 267€

Return flights