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

Return flights

02 Dec - 09 Dec	easyJet
09 Dec - 13 Dec	easyJet
09 Dec - 11 Dec	easyJet
08 Dec - 13 Dec	easyJet
09 Dec - 16 Dec	easyJet
08 Dec - 11 Dec	easyJet
02 Dec - 13 Dec	easyJet
10 Dec - 16 Dec	easyJet
03 Dec - 13 Dec	easyJet
31 Dec - 06 Jan	easyJet
02 Dec - 08 Dec	easyJet
31 Dec - 09 Jan	easyJet
31 Dec - 07 Jan	easyJet
31 Dec - 04 Jan	easyJet
20 Dec - 03 Jan	Ryanair
25 Dec - 01 Jan	KLM
30 Dec - 05 Jan	Ryanair
31 Dec - 02 Jan	easyJet
26 Dec - 01 Jan	Ryanair
27 Dec - 01 Jan	Ryanair

Also check the deals for one-way flights from Lisbon to Keflavik 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 Lisbon to Keflavik in December from $203

Return flights