AirHint found the following cheapest return flights from London (LCY) to Keflavik (KEF) in August 2025 (see full year).

Return flights

29 Aug - 08 Sep	Lufthansa
14 Aug - 18 Aug	SWISS
15 Aug - 18 Aug	SWISS
13 Aug - 20 Aug	KLM
10 Aug - 17 Aug	KLM
06 Aug - 19 Aug	SWISS
28 Aug - 04 Sep	SWISS
25 Aug - 28 Aug	KLM
25 Aug - 07 Sep	KLM
25 Aug - 29 Aug	KLM
10 Aug - 18 Aug	KLM
01 Aug - 07 Aug	KLM
01 Aug - 17 Aug	KLM
29 Aug - 04 Sep	Lufthansa
27 Aug - 01 Sep	KLM
28 Aug - 03 Sep	KLM
29 Aug - 07 Sep	Lufthansa
28 Aug - 02 Sep	SWISS
27 Aug - 02 Sep	SWISS
29 Aug - 01 Sep	British Airways

Also check the deals for one-way flights from London to Keflavik in August.

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 London to Keflavik in August from $454

Return flights