Marek Jan Sanak (born 24 November 1958) is a Polish geneticist and molecular biologist, professor of medical sciences, Head of the Department of Molecular Biology and Clinical Genetics of the Jagiellonian University Medical College, Head of the Department of Biochemical and Molecular Diagnostics at the University Hospital in Kraków, the Jagiellonian University Rector's Plenipotentiary for Science and Development in the Medical College, member of the Polish Academy of Learning, and the author of more than 230 original research papers published in peer reviewed journals.

[1][2] That year, he started to work as a junior assistant at the Department of Medical Genetics at the Pediatrics Institute in Kraków.

His doctoral thesis focused on the congenital disorders in children, taking into account the distribution of atmospheric pollution with heavy metals.

Between 1993–2005 he worked as an assistant professor at the Institute of Pharmacology of the Polish Academy of Sciences, at the Department of Brain Biochemistry headed by Jerzy Vetulani.

He was appointed the Jagiellonian University Rector's Plenipotentiary for Science and Development in the Medical College for the term 2016–2020.

Sanak authored or co-authored more than 230 original research papers in international peer reviewed journals.

[3] He was the author of the discovery of the genetic polymorphism of the promoter region of the gene of the leukotriene C4 synthase; and he participated in establishing the relationship between genetic overexpression caused by the presence of the altered allele of that gene and the overproduction of cysteinyl leukotrienes in bronchial asthma.