State Highway 73 is a major east-west South Island state highway in New Zealand connecting Christchurch on the east coast with Cass/Hokitika via the Southern Alps. It is mostly two lane, with some single-lane bridges north of Springfield but is mostly dual carriageway in Christchurch. The fourth and fifth-highest points of New Zealand's state highway network are on this road at Porters Pass and Arthur's Pass respectively.

The New Zealand state highway network is the major national highway network in New Zealand. Nearly 100 roads in the North and South Islands are state highways. All state highways are administered by the NZ Transport Agency.