Wander Johannes de Haas (2 March 1878 – 26 April 1960) was a Dutch physicist and mathematician.

He was the son of Albertus de Haas, principal of the Teacher's College in Middelburg, and Maria Efting.

[1] 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.

Then he returned to the Netherlands, worked as a schoolteacher in Deventer, a conservator of the Teylers Museum in Haarlem, and then a physics professor in Delft Technical School and University of Groningen.