Matanuska-Susitna Valley shown shaded in red north of Anchorage

Matanuska-Susitna Valley (known locally as the Mat-Su Valley) is an area in south central Alaska south of the Alaska Range north and northeast of Anchorage. It is over 23,000 mile² (60,000 km²) in size, comprising the valleys of the Matanuska and Susitna rivers. It is one of the most settled areas in Alaska and includes the towns of Wasilla, Palmer, Houston, Big Lake, Willow and Talkeetna.

The valley and is rimmed by three major mountain ranges: the Alaska Range, the Talkeetna Mountains and the Chugach Mountains. The surrounding mountains include many mountain passes, as well as working and extinct gold mines. Like many parts of Alaska, the Matanuska-Susitna Valley was carved by glaciers which left many small and large lakes. Both the Matanuska and Susitna rivers are major salmon spawning streams.

The valley was settled by many homesteaders as part of an experiment in the 1930s. The current population includes a diverse group of people both Alaska Natives and "sourdoughs".

The Susitna, Matanuska, and Knik rivers are all very active glacial streams terminating in the silty Cook Inlet. The rivers convey large amounts of glacial silt that lends itself well to farming. The valley is one of the few areas in Alaska that supports agriculture.

The region is also home to the valley-wide Matanuska-Susitna College and the Mat-Su Valley Frontiersman newspaper.

The valley is also home to the annual Talkeetna Bluegrass Festival, Alaska's largest camping-oriented music festival. 2006 marked the 25th anniversary of the Festival.