Nobel laureates with a physics Ph.D. from Leiden University
1981
physics prize

Nico Bloembergen
Ph.D. 1948 with Cor Gorter
Nuclear Magnetic Relaxation

1975
economics prize

Tjalling Koopmans
Ph.D. 1936 with Hans Kramers
Linear regression analysis of economic time series

1969
economics prize

Jan Tinbergen
Ph.D. 1929 with Paul Ehrenfest
Minimumproblemen in de natuurkunde en de economie

1910
physics prize

Johannes van der Waals
Ph.D. 1873 with Pieter Rijke
Over de continuiteit van den gas- en vloeistoftoestand

1902
physics prize

Hendrik Lorentz
Ph.D. 1875 with Pieter Rijke
Over de theorie der terugkaatsing en breking van het licht

1902
physics prize

Pieter Zeeman
Ph.D. 1893 with Heike Kamerlingh Onnes
Metingen over het verschijnsel van Kerr

Outside of physics, there are two more Leiden Ph.D. alumni who went on to win a Nobel prize:

Tobias Asser, 1860 Ph.D. in law, 1911 Nobel peace prize.

Niko Tinbergen, 1932 Ph.D. in biology, 1973 Nobel prize in medicine.