The letter S is pronounced the same as in English (“some, sing”).[1]
  • sandur, bless, sæll
The name of the letter is “ess”, same as in English

There are a few other sounds in Icelandic that to many foreigners sound like an S but aren’t. Those are:

The Þ sound: þannig, með

The breathy R sound: góður, hratt

The breathy L sound: vel, hlægja