Johann Theodor Eller (von Brockhausen) (29 November 1689 – 13 September 1760) was a German physician, mineralogist and chemist who served in the Prussian court. Eller followed the beliefs of the day that heat was an element. Lavoisier read his works on air and fire. In his medical research he claimed that copper in cooking utensils was harmful. Eller married Catherine Elizabeth Burckhard (d. 1751) in 1721 and after in 1753 he married Henrietta Catherine Rosen. Eller published two books: