Arenius was born in the parish of Bro in
Uppland, Sweden. His father was a vicar in
Upplands-Bro. After a period of theology studies at
Uppsala University, he studied art under
David von Krafft (1655–1724). In 1729, he went to the
United Kingdom where he was exposed to the art of portrait painters
Godfried Kneller (1646–1723) and
Mikael Dahl (1659–1743). Returning to Sweden in 1736, he was named court painter by King
Frederick I of Sweden. He died at
Stockholm in 1766. His portraits and
miniatures in oil are much esteemed, and are to be found in all the public galleries, as well as in the best private collections, in Sweden. Many of them have been engraved.{{cite web|url= https://runeberg.org/sbh/a0042.html |title= Olof Arenius ==Gallery==