The state government says thousands of new homes will be built as part of a large scale land release across Adelaide's northern and southern suburbs.

At least 23,700 homes will be built on land to be rezoned as residential at Hackham and Sellicks Beach in Adelaide's south and at Dry Creek and Concordia in the north.

The government said at least 15 per cent of the homes will be designated as affordable housing.

Premier Peter Malinauskas said the housing market "should be defined by choice".

"I think some people might prefer a denser-style living arrangement, potentially closer to the city, but other families will want the ability to be able to raise their children in a home with a backyard," he said.

"And we want to make sure that choice is accessible to everybody and land supply is critical to that.

"If we don't have enough land on the market, then we won't have homes being built.

"And if we don't have homes being built then the market starts to become completely inaccessible to families."

Treasurer Stephen Mullighan said releasing more land to the market would bring "housing affordability into the reach of more South Australians".

"Housing affordability has become that much harder, particularly in the last two years," he said.

The state government said valuer-general data showed the median house price in Adelaide has reached $670,000 — a 38.1 per cent increase in three years.

And a recent report from Domain showed Adelaide was the only capital city market with new record high house and unit prices, bucking a national downward trend.

"It [the land release] ensures that house price growth can be maintained but not in such a way that it compromises the ability for a young family to have ownership into the future," Mr Malinauskas said.