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

Return flights

25 Aug - 27 Aug	ITA Airways
27 Aug - 03 Sep	KLM
13 Aug - 20 Aug	KLM
20 Aug - 27 Aug	KLM
28 Aug - 04 Sep	KLM
06 Aug - 13 Aug	KLM
13 Aug - 16 Aug	KLM
27 Aug - 04 Sep	KLM
06 Aug - 10 Aug	KLM
13 Aug - 03 Sep	KLM
14 Aug - 22 Aug	KLM
14 Aug - 18 Aug	KLM
06 Aug - 11 Aug	KLM
25 Aug - 28 Aug	KLM
28 Aug - 05 Sep	KLM
29 Aug - 05 Sep	KLM
22 Aug - 04 Sep	SWISS
25 Aug - 01 Sep	KLM
31 Aug - 08 Sep	KLM
31 Aug - 04 Sep	KLM

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 347€

Return flights