Janssen is a Dutch patronymic surname cognate to the English surname Johnson.
It is the 7th most common name in the Netherlands and the most common (over 131,000 people), when combined with the spelling variant Jansen.
As of 2014, 45.3% of all known bearers of the surname Janssen were residents of the Netherlands (frequency 1:281), 26.9% of Germany (1:2,249), 11.5% of the United States (1:23,667), 9.4% of Belgium (1:926), 1.4% of Australia (1:12,720) and 1.2% of Canada (1:23,187).
In the Netherlands, the frequency of the surname was higher than national average (1:281) in the following provinces: In Belgium, the frequency of the surname was higher than national average (1:926) only in one region: Flemish Region (1:696).
In Germany, the frequency of the surname was higher than national average (1:2,249) in the following states:[1]