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

Return flights

22 Dec - 28 Jan	Qantas
31 Dec - 21 Jan	Qantas
02 Dec - 08 Dec	Spirit Airlines
08 Dec - 12 Dec	Spirit Airlines
04 Dec - 20 Dec	Frontier Airlines
29 Dec - 23 Jan	Qantas
02 Dec - 09 Dec	Spirit Airlines
07 Dec - 21 Dec	Frontier Airlines
07 Dec - 23 Dec	Frontier Airlines
31 Dec - 11 Jan	United
10 Dec - 10 Jan	Hawaiian Airlines
26 Dec - 12 Jan	Etihad Airways
27 Dec - 12 Jan	Frontier Airlines
20 Dec - 10 Jan	Qantas
20 Dec - 07 Jan	Qantas
26 Dec - 11 Jan	Etihad Airways

Also check the deals for one-way flights from Chicago to Sydney 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 Sydney in December from $946

Return flights