Harald Feller was the son of the Swiss historian Richard Feller.
In 1944 he replaced Maximilian Jaeger ( 1915-1999 ) as head of the Swiss legation in Budapest, Hungary. He supported Carl Lutz in the rescue of Jews under Swiss protection. Feller worked closely with the other neutral embassies to achieve together to stop the persecution and deportation of Jews with a permanent pressure on the Horthy and Sztojay governments. Feller protected members of the Swedish legation, which target group of the Arrow Cross were ready by asking them fake Swiss passes and accommodation. Towards the end of the war hidden Feller dozens of Jews in the basement of his consular residence in Budapest. In February 1945, the Soviets arrested Feller and Maximilian Jaeger and sent them to Moscow, along with other Swiss nationals. Both were in February 1946 in exchange for two pilots who crashed in Switzerland, returned.
He received the 1999 Yad Vashem honors the Righteous among the Nations.