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

Return flights

11 Dec - 13 Dec	easyJet
11 Dec - 18 Dec	easyJet
10 Dec - 17 Dec	easyJet
04 Dec - 06 Dec	easyJet
14 Dec - 08 Jan	Icelandair
18 Dec - 18 Jan	easyJet
14 Dec - 07 Jan	Icelandair
07 Dec - 14 Dec	easyJet
18 Dec - 24 Dec	easyJet
07 Dec - 14 Dec	Icelandair	direct
11 Dec - 18 Dec	Icelandair	direct
28 Dec - 01 Jan	easyJet
28 Dec - 01 Jan	Icelandair	direct
18 Dec - 03 Jan	easyJet
26 Dec - 30 Dec	Wizz Air Malta
21 Dec - 04 Jan	easyJet
23 Dec - 29 Dec	Wizz Air
18 Dec - 18 Jan	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 $241

Return flights