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

Return flights

22 Sep - 29 Sep	Air Canada
30 Sep - 08 Oct	Air Canada
07 Sep - 14 Sep	TAP	direct
08 Sep - 18 Sep	TAP	direct
06 Sep - 15 Sep	TAP	direct
21 Sep - 02 Oct	TAP	direct
14 Sep - 21 Sep	TAP	direct
25 Sep - 02 Oct	TAP	direct
06 Sep - 22 Sep	TAP	direct
27 Sep - 07 Oct	Spirit Airlines
29 Sep - 04 Oct	Spirit Airlines
27 Sep - 05 Oct	Icelandair
10 Sep - 14 Oct	Spirit Airlines
13 Sep - 28 Sep	Icelandair
12 Sep - 21 Sep	Spirit Airlines
30 Sep - 05 Oct	Icelandair
17 Sep - 24 Sep	Spirit Airlines
13 Sep - 24 Sep	Icelandair
30 Sep - 10 Oct	Spirit Airlines
26 Sep - 03 Oct	Spirit Airlines

Also check the deals for one-way flights from Chicago to Lisbon in September.

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 September from $439

Return flights