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

Return flights

01 Dec - 15 Dec	Qantas
02 Dec - 12 Dec	Hawaiian Airlines
07 Dec - 23 Dec	Air Canada
04 Dec - 14 Dec	Frontier Airlines
08 Dec - 17 Dec	Hawaiian Airlines
08 Dec - 30 Dec	Qantas
10 Dec - 10 Jan	Spirit Airlines
12 Dec - 11 Jan	Frontier Airlines
25 Dec - 08 Jan	Hawaiian Airlines
27 Dec - 07 Jan	IndiGo
22 Dec - 12 Jan	United
18 Dec - 12 Jan	Qantas
23 Dec - 28 Dec	Fiji Airways
20 Dec - 10 Jan	Sun Country Airlines
20 Dec - 07 Jan	Sun Country Airlines
18 Dec - 06 Jan	Sun Country Airlines
23 Dec - 03 Jan	Frontier Airlines

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 734€

Return flights