Sem or Semsbyen is a village in Tønsberg Municipality in Vestfold county, Norway.

The village of Vear lies about 3 kilometres (1.9 mi) to the southeast of Sem, along the shore of the Tønsbergfjorden.

[3] The village lies along the border with Sandefjord Municipality to the southwest (in fact, a small portion of the urban area of Sem crosses over the border and has about 50 residents in the neighboring municipality).

King Harald Fairhair chose to install his son Bjorn Farmann as the master of the estate.

The first element is sær which means "sea" or "ocean", likely referring to the local Tønsbergfjorden.