Peder Pedersen Syv (also spelled Siuf) or in Latin Petrus Petri Septimius (February 22, 1631 – February 17, 1702) was a Danish philologist, folklorist and priest, known for his collections of Danish proverbs and folksongs, and his contributions to the development of Danish as a written language.
Peder Syv's father was an indentured peasant in the village of Syv (today called Kirke Syv) near Roskilde - probably one Peder Olufsen, and his mother Anna Mortensdatter. The family seems to have been fairly well off for their social class, and several of Peder's siblings were able to take up professions. One of his brothers seems to have been an uneasy soul, and died on a trip to the Danish East Indian colonies in 1674.
In 1648 Syv entered the Latin school at Roskilde, where he lived at the cloister, holding the office of deputator, an advanced student charged with overseeing the youths. He graduated in 1653 along with his friend Laurids Olufsen Kok, who became one of his allies in the promotion of Danish language. He studied briefly at the University of Copenhagen, until it temporarily closed in 1654 due to a plague outbreak in Copenhagen. But Syv had already received his bachelor's degree and went on to teach Latin at the Metropolitan school in Copenhagen. In 1658 he became rector at Næstved. He seems to have enjoyed teaching music there as is attested in a letter to musicologist Hans Mikkelsen Ravn, thanking him for ten copies of his work Heptachordum Danicum. Næstved was also the abode of noble woman Anna Gøye, who owned one of Denmark's largest libraries to which she gave Peder Syv access. He was also sought out as a baptismal godfather for many locals.
In 1664, he became parish priest in Hellested close to Stevns in southern Zealand. In order to qualify to take over the farm that came with the office, he married the widow of the former priest, Karen Andersdatter Hoff. She had one son, Hans Hansen Hellested, whom Syv adopted as his own. Together they had three daughters, Ide, Vibeke and Anna Kirstine, the last of whom married her father's successor as priest in Hellested, Rudolf Moth Bagger. In 1699, Syv became a widower and noted in his journal "[today] died my most dear and virtuous wife Karen Andersdatter Hoff".