AirHint found the following cheapest return flights from Denver (DEN) to Lisbon (LIS) in July 2025 (see full year).

Return flights

16 Jul - 24 Jul	Frontier Airlines
18 Jul - 22 Jul	Turkish Airlines
15 Jul - 18 Jul	Frontier Airlines
15 Jul - 17 Jul	Frontier Airlines
15 Jul - 25 Jul	Frontier Airlines
26 Jul - 03 Aug	Frontier Airlines
07 Jul - 14 Jul	Frontier Airlines
04 Jul - 10 Jul	Frontier Airlines

Also check the deals for one-way flights from Denver to Lisbon in July.

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 Denver to Lisbon in July from 733€

Return flights