What Norse god is Sunday named for?

Sunday is as obvious as it gets. It means day of the Sun and isn't named after a deity. In Latin it's Dies Solis. In Old Norse it was sunnudagr. The Norse personification of the Sun was also called Sol or Sunna.

It should be noted that the Norse Days of the week were named to match the Latin Counterparts.

Example: Wednesday = Odin's Day = Dies Mercurii Mercury and Odin were both patrons of Travelers and often disguised themselves as old men while traveling.

Another: Thursday = Thor's Day = Dies Jovis Thor and Jove (Jupiter) were both gods of thunder and lightning.

Finally: Tuesday = Tyr's Day = Dies Martis Mars and Tyr were both gods of war.