Family name Lonnroth (Lonnroth 
) , across the world, is a rare surname. The surname Lonnroth is characteristic of Finland, where it is quite a rare surname, Sweden, where it is a rare surname, and Switzerland. Not in comparison with a country's population, this name is the most popular in Finland, Sweden, and the United States.
| VARIANT | COUNTRY |
|---|---|
| Lonnroth | Sweden, Norway, Finland, Switzerland, United States |