Josip Klasancije Schlosser pl. Klekovski (1801–1882) was a Croatian physician, alpinist and botanist.

Together with Ljudevit Farkaš Vukotinović, he was an author of Flora croatica (1869), the main work for the knowledge of plants in Croatia. He was the most prominent 19th century botanist and explorer of Risnjak mountain, and wrote numerous publications about Risnjak's flora.