Hammarskjöld, also Hammarskiöld, is a Swedish noble family, enrolled in Riddarhuset ("House of Nobility") with the number of 135.
The founder of the family was Peder Mikaelsson (c. 1560–1646), the Governor of Borgholm Castle. He fought for King Sigismund at Stångebro in 1598 and was knighted in 1610 with the name of Hammarskiöld. He was married twice. His first wife was Beata Körning, daughter of the slottslov [ castle commander ] Erik Matsson Körning and Kjerstin Hand. His second wife, a cousin of Beata, was Christina Stjerna, the daughter of Peder Månsson Stjerna (No. 77 in Riddarhuset) and Karin Hand. The two marriages produced children but the issue from his first wife went out early on the "sword side" [ svärdssidan = without any male heirs ] .
As early as 1607 Peder Mikaelsson Hammarskiöld received as his properties the manors in the present Oskarshamn Municipality – Misterhult, Virbo and Fårbo – and, in the present Vimmerby Municipality, Tuna, all in the modern Kalmar County for providing five fully armed men for the defense. Tuna is still a family estate for the Hammarskjölds, and the church there houses the family mausoleum for them. The family was introduced to Riddarhuset in 1628.
The son of the second marriage, Major Arvid Hammarskjöld, married Anna Dorothea Patkull. The Hammarskjöld dynasty continued with their son, Colonel Carl Gustaf Hammarskjöld, who married Baroness Hedvig Ulfsparre of Broxvik, whose mother belonged to the Stake family (No. 47 in Riddarhuset).
A younger branch of the family has been partners and managing directors of Skultuna Messingbruk, a Swedish manufacturer of cuff links in Skultuna near Västerås in Västmanland, by intermarriage with the Adlerwald family.
In 2014, there are 61 persons who bear the Hammarskjöld/Hammarskiöld surname in Sweden.