Markus Reiner (Hebrew: מרכוס ריינר, born 5 January 1886, died 25 April 1976) was an Israeli scientist and a major figure in rheology.

After the First World War, he immigrated to Mandatory Palestine, where he worked as a civil engineer under the British mandate.

In his honour the Technion later instituted the Markus Reiner Chair in Mechanics and Rheology.

Reiner was not only a major figure in rheology, he along with Eugene C. Bingham coined the term[2] and founded a society for its study.

As well as the term rheology, and his publications, he is known for the Buckingham-Reiner Equation, the Reiner-Riwlin Equation, and Reiner-Rivlin fluids, the Deborah number and the Teapot effect – an explanation of why tea runs down the outside of the spout of a teapot instead of into the cup.