AirHint found the following cheapest return flights from Chicago (ORD) to Lisbon (LIS) in August 2025 (see full year).

Return flights

19 Aug - 28 Aug	United
18 Aug - 26 Aug	British Airways
19 Aug - 26 Aug	British Airways
20 Aug - 26 Aug	SWISS
17 Aug - 06 Sep	United
18 Aug - 25 Aug	United
22 Aug - 28 Aug	TAP	direct
30 Aug - 03 Sep	Aer Lingus
22 Aug - 13 Sep	Aer Lingus
25 Aug - 20 Sep	Aer Lingus
18 Aug - 24 Aug	SWISS
20 Aug - 28 Aug	Air France
21 Aug - 30 Aug	United
30 Aug - 20 Sep	Aer Lingus
30 Aug - 07 Sep	Aer Lingus
29 Aug - 04 Sep	TAP	direct
30 Aug - 05 Sep	TAP	direct
30 Aug - 08 Sep	Spirit Airlines
29 Aug - 05 Sep	TAP	direct
18 Aug - 24 Aug	TAP	direct

Also check the deals for one-way flights from Chicago to Lisbon 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 Chicago to Lisbon in August from 491€

Return flights