Wander Johannes de Haas (2 March 1878, Lisse – 26 April 1960, Bilthoven) was a Dutch physicist and mathematician. He is best known for the Shubnikov–de Haas effect, the de Haas–van Alphen effect and the Einstein–de Haas effect.

Wander de Haas was born in Lisse, a small town near Leiden. He was the son of Albertus de Haas, principal of the Teacher's College in Middelburg, and Maria Efting. On 22 December 1910 he married Geertruida Luberta Lorentz, the eldest daughter of Hendrik Lorentz. They had two daughters and two sons.

After attending high school in Middelburg, de Haas started paralegal studies in 1895. After completion of two of three parts of the examinations and having worked in a lawyer's office for some time, he decided to change career and become a physicist instead. After passing the qualifications exams for admission to University, he started to study physics at the University of Leiden in 1900 under Heike Kamerlingh Onnes and Johannes Petrus Kuenen. He earned his doctorate in 1912, under Kamerlingh Onnes, with a thesis entitled: Measurements on the Compressibility of Hydrogen. An example of the equipment (an electromagnet of c.1930) used for his low-temperature research can be seen in the Boerhaave Museum, the history of science museum in Leiden.