Svelvik is a town and municipality in Vestfold county, Norway. The administrative centre of the municipality is the town of Svelvik.The town of Svelvik was separated from the rural municipality of Strømm to become a municipality of its own in 1845. The two municipalities were merged back together on 1 January 1964.
The Norse form of the name was Sverðvík. The first element is sverð n 'sword', the last element is vík f 'cove, wick'. A neighbouring farm has the name Sverstad (Norse Sverðstaðir). The word sverð is probably referring to the promontory ridge Ryggen ('the back') in Hurum: This ridge is lying right opposite Svelvik and Sverstad, and it is almost (like a sword) cutting the Drammensfjord in two parts.
The coat-of-arms is from modern times. They were granted on 4 September 1964. Svelvik is an important harbor and its economy is thus also based on the harbor. The arms show a gold-colored trident on a red background, as a symbol for the sea.