Seddon is a small town in Marlborough, New Zealand. It is located on State Highway 1, 25 kilometres south of Blenheim and 20 km north of Ward. Seddon is located close to the mouths of the Awatere and Blind Rivers, and also close to the Lake Grassmere salt works. Salt and lime are major local industries, and the Awatere Valley is a developing wine region. The population was 510 in the 2006 Census, an increase of 36 from 2001.
The town's best known structure is a joint single-lane road-rail bridge spanning the Awatere River which was in service until October 2007. A two lane road bridge has replaced the road bridge component. The railway line continues over the old historic bridge which is the Main North Line and a daily service in each direction of the TranzCoastal passenger express stops in Seddon.