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

Return flights

29 Sep - 06 Oct	Icelandair
08 Sep - 15 Sep	Icelandair
18 Sep - 25 Sep	Icelandair
02 Sep - 09 Sep	United
04 Sep - 11 Sep	United
14 Sep - 21 Sep	United
23 Sep - 30 Sep	United
16 Sep - 23 Sep	United
26 Sep - 03 Oct	United
12 Sep - 20 Sep	KLM
12 Sep - 19 Sep	Icelandair
20 Sep - 27 Sep	Scandinavian Airlines

Also check the deals for one-way flights from Chicago to Oslo 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 Oslo in September from 383€

Return flights