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

Return flights

12 Dec - 16 Dec	easyJet
01 Dec - 07 Dec	easyJet
14 Dec - 17 Dec	easyJet
15 Dec - 18 Dec	Wizz Air Malta
29 Dec - 02 Jan	Fly Play	direct
19 Dec - 22 Dec	Fly Play	direct
19 Dec - 05 Jan	Fly Play	direct
19 Dec - 02 Jan	Fly Play	direct
22 Dec - 02 Jan	Fly Play	direct
24 Dec - 30 Dec	easyJet
28 Dec - 04 Jan	easyJet
26 Dec - 01 Jan	easyJet
25 Dec - 30 Dec	Lufthansa
28 Dec - 04 Jan	Icelandair	direct
21 Dec - 28 Dec	easyJet
21 Dec - 28 Dec	Icelandair	direct

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 $173

Return flights