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

Return flights

03 Dec - 10 Dec	easyJet
04 Dec - 11 Dec	easyJet
04 Dec - 18 Dec	easyJet
07 Dec - 18 Dec	easyJet
19 Dec - 22 Dec	Fly Play
19 Dec - 22 Dec	Fly Play	direct
19 Dec - 02 Jan	Fly Play	direct
19 Dec - 05 Jan	Fly Play	direct
28 Dec - 05 Jan	easyJet
19 Dec - 26 Dec	Fly Play	direct
27 Dec - 03 Jan	easyJet
26 Dec - 03 Jan	Fly Play
28 Dec - 04 Jan	easyJet
04 Dec - 18 Dec	Icelandair	direct
07 Dec - 18 Dec	Icelandair	direct
04 Dec - 11 Dec	Icelandair	direct
21 Dec - 04 Jan	Fly Play
28 Dec - 04 Jan	Icelandair	direct
21 Dec - 04 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 133€

Return flights