Robert Adolph Armand Tigerstedt (28 February 1853 – 12 February 1923) was a Finnish-born medical scientist and physiologist who, with his student Per Bergman, discovered renin at the Karolinska Institute, Stockholm in 1898.
Renin is a component of the renin–angiotensin system which regulates blood pressure, salt and water homeostasis and is an important therapeutic target.
Tigerstedt is also recognised as an educator, author and social campaigner.