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

Return flights

15 Sep - 21 Sep	TAP	direct
06 Sep - 15 Sep	TAP	direct
25 Sep - 29 Sep	TAP	direct
15 Sep - 22 Sep	TAP	direct
20 Sep - 26 Sep	TAP	direct
22 Sep - 01 Oct	TAP	direct
26 Sep - 15 Oct	TAP	direct
11 Sep - 15 Sep	TAP	direct
23 Sep - 02 Oct	Aer Lingus
25 Sep - 09 Oct	TAP	direct
24 Sep - 01 Oct	Delta
08 Sep - 21 Sep	Aer Lingus
08 Sep - 12 Sep	Icelandair
16 Sep - 18 Sep	Aer Lingus
24 Sep - 13 Oct	United
18 Sep - 22 Sep	TAP	direct
28 Sep - 10 Oct	Aer Lingus
10 Sep - 14 Oct	Lufthansa
30 Sep - 07 Oct	United
27 Sep - 04 Oct	TAP	direct

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 424€

Return flights