Isaac Salmonsen (1846 – 1910) was a Danish bookseller and publisher.

He established the publishing house Brødrene Salmonsen in 1871, along with his brother.

He is particularly known for publishing the Danish encyclopedia, Salmonsens Store Illustrerede Konversationsleksikon.

The first edition of the encyclopedia came in nineteen volumes between 1893 and 1911.

This business-related Danish biographical article is a stub.