AirHint found the following cheapest return flights from Chicago (ORD) to Brussels (BRU) in December 2025 (see full year).

Return flights

06 Dec - 13 Dec	Scandinavian Airlines
05 Dec - 08 Dec	Scandinavian Airlines
01 Dec - 05 Dec	Frontier Airlines
14 Dec - 24 Dec	Spirit Airlines
13 Dec - 18 Dec	Aer Lingus
18 Dec - 22 Dec	Spirit Airlines
25 Dec - 01 Jan	Frontier Airlines
17 Dec - 19 Dec	Frontier Airlines
19 Dec - 28 Dec	Frontier Airlines
24 Dec - 03 Jan	Brussels Airlines
25 Dec - 01 Jan	Lufthansa	direct
27 Dec - 04 Jan	United	direct
06 Dec - 13 Dec	Lufthansa	direct
05 Dec - 08 Dec	Lufthansa	direct
25 Dec - 02 Jan	Aer Lingus

Also check the deals for one-way flights from Chicago to Brussels in December.

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 Brussels in December from 513€

Return flights