Sigvatr Þórðarson (Sighvatr Þórðarson, Sigvat Tordarson) or Sigvat the Skald (995-1045) was an Icelandic skald. He was a court poet to King Olaf II of Norway, as well as Canute the Great, Magnus the Good and Anund Jacob, by whose reigns his floruit can be dated to the earlier eleventh century. Sigvatr was the best known of the court skalds of King Olaf and also served as his marshal (stallare).
Approximately 160 verses of Sigvatr's poetry have been preserved, more than any for other poet from this period. The style of Sigvat's poems is simpler and clearer than that which generally characterises older compositions. Although his verse is still dense, he uses fewer complex poetic circumlocutions than many of his predecessors, and as a Christian poet, he by and large avoids allusions to pagan mythology.
Most of his surviving poems were texts that praised King Olaf. Many of the poems from St. Olaf's saga in Heimskringla are by Sigvatr. Víkingarvísur, composed c. 1014-15, is the oldest of the surviving long poems attributed to him. The poem tallies King Olaf’s battles on his Viking expeditions until 1015, when he returned to Norway to carve out a kingdom for himself.
In Nesjavísur, the next oldest poem by Sigvatr, the skald describes the naval battle between Olaf and Sveinn Hákonarson at the Battle of Nesjar outside Brunlanes in 1016, the key moment in Olaf's ascent to power in Norway. 
- Víkingarvísur- on the early deeds of King Olaf
- Nesjavísur- on the Battle of Nesjar
- Austrfararvísur- on a diplomatic journey to Sweden
- Drápa um Óláf Konung - on King Olaf
- Vestrfararvísur ("Western travel verses") - on a journey to Great Britain
- Kvæði um Erling Skjalgsson - on Erlingr Skjalgsson
- Flokkr um Erling Skjalgsson - on Erlingr Skjalgsson
- Tryggvaflokkr - on Tryggve the Pretender
- Kvæði um Ástríði Dróttningu - about Queen Astrid
- Knútsdrápa- in memory of King Canute the Great
- Bersöglisvísur- reprimand to King Magnus
- Erfidrápa Óláfs helga- in memory of King Olaf
- Brot - fragments
- Sturlason, Snorre (2004). Heimskringla or the Lives of the Norse Kings. Kessinger Publishing. p. 225. ISBN 0-7661-8693-8.
- Sigvat Tordarson (Store norske leksikon)
- Sigvat Tordsson – utdypning (Store norske leksikon)
- Fell, Christine, 1981: Víkingarvísur. In: Speculum Norroenum. Norse Studies in Memory of Gabriel Turville Petre. Ed. U. Dronke. Odense. Pp. 106–22
- Víkingarvísur (Skaldic Poetry of the Scandinavian Middle Ages)
- Nesjavísur (Skaldic Poetry of the Scandinavian Middle Ages)
- Whaley, Diana (editor) Poetry from the Kings' Sagas 1, From Mythical Times to c. 1035 (Brepols Publishers. 2013) ISBN 978-2-503-51896-1
- O'Donoghue, Heather (2005) Skaldic Verse and the Poetics of Saga Narrative (Oxford University Press) ISBN 978-0199267323