Jakob Björck was a Swedish portrait painter and copyist.

In the early stages of his career, Björck is reported to have been a pupil of Johan Henrik Scheffel; however, this is uncertain. He worked in the studio of pastel painter Gustav Lundberg between 1750 and 1774. In 1774, Björck married Cicilia Gren (1723 or 1724–1811).

Oil copies of Lundberg's pastels are usually attributed to Björck, despite several other assistants being employed in the studio at the time: Per Cogell (later a city painter in Lyon), Adolf Hall, Jonas Forsslund and a pastel painter named Pettersson. In addition, Lundberg had so many orders at times that he delegated the copy orders to other artists – Johan Henrik Scheffel and Fredrik Brander.

From 1774 Björck had his own production, where he mainly copied the works of others, such as one of Jean-Baptiste Oudry's door lintels in the Royal Palace, Hunting dog with two grouse, which he signed Iacob Björck px on the stretcher bar. He had the opportunity to paint King Gustav III in the Life Guards' uniform with the revolutionaries' armband and partly in Swedish costume, both in magnificent royal frames. In general, however, it is assumed that he copied from the now-lost or destroyed works by Lundberg. Björck had the title HofCopist, probably at Lundberg's insistence in order to avoid problems with the painting office.

His own style is rough compared to Lundberg's light elegance. This is evident from the portraits of King Gustav III and Adolf Ludvig Stierneld below in the gallery. Over time, his production became purely artisanal and the copies of the many stereotypical portraits of Lundberg's last days are consistently dry and lifeless. The portraits of Gustavus Gyllenborg, his wife Petronella Hultman and the copy of Lundberg's self-portraits in the below gallery can be seen as an example of this. Björck's copies of Lundberg's portraits during the 21st century sold for anything from 20,000 kr to 180,000 kr, depending on how decorated the frame was. Portraits of women and children are generally valued higher than men's portraits.