Nikolaas Tinbergen (April 15, 1907 - December 21, 1988) was a noted ethologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl Von Frisch and Konrad Lorenz for their discoveries concerning organization and elicitation of individual and social behaviour patterns. Born in The Hague, Netherlands, he is also noted as the brother of Jan Tinbergen, who won the first Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel. He had a third eminent brother, Luuk Tinbergen.

He is well known for originating the four questions he believed should be asked of any animal behaviour, which were:

1. Function: how does the behaviour impact on the animal's chances of survival and reproduction?
2. Causation: what are the stimuli that elicit the response, and how has it been modified by recent learning?
3. Development: how does the behaviour change with age, and what early experiences are necessary for the behaviour to be shown?
4. Evolutionary history: how does the behaviour compare with similar behaviour in related species, and how might it have arisen through the process of phylogeny?

They are still considered as the cornerstone of modern ethology.