Sigtrygg II Silkbeard Olafsson (also
Sihtric,
Sitric and
Sitrick in Irish texts; or
Sigtryg and
Sigtryggr in Scandinavian texts) was a
Hiberno-Norse king of Dublin (possibly AD 989–994; restored or began 995–1000; restored 1000 and abdicated 1036) of the
Uí Ímair dynasty. He was caught up in the abortive Leinster revolt of 999–1000, after which he was forced to submit to the
King of Munster,
Brian Boru. His family also conducted a double marriage alliance with Boru, although he later realigned himself with the main leaders of the Leinster revolt of 1012–1014. He has a prominent role in the 12th-century Irish
Cogadh Gaedhil re Gallaibh and the 13th century Icelandic
Njal's Saga, as the main Norse leader at the
Battle of Clontarf in 1014.