Saul Adler OBE FRS (Hebrew: שאול אדלר; May 17, 1895 – January 25, 1966) was an Israeli expert on parasitology.

From 1917 until 1920, Adler served in the Royal Army Medical Corps, attaining the rank of captain, serving in the Middle East, where he developed his first taste into research into tropical medicine, which he commenced studying after his military service, initially in Liverpool.

Later that year, he emigrated to Mandate Palestine and started working in Hadassah Hospital, becoming director of the department of parasitology in 1927.

In 1930, in conjunction with Israel Aharoni, Adler had three Syrian hamsters brought back from Syria and successfully bred them as laboratory animals.

In the 1940s he was a leader in developing a leishmaniasis vaccine using live parasites, a practice widespread in Israel and Russia until the 1980s, when large-scale clinical trials showed that the practice led to long-term skin lesions, exacerbation of psoriasis, and immunosuppression in some people.