Mančinskis is to pursue a career outside Latvia. He had been the bank's CEO for seven years.
Board member Reinis Rubenis will assume his post on September 12.
Mančinskis originally worked in investment banking and worked at different posts of Swedbank Group, including Swedbank Russia.
"I am sure that Reinis Rubenis, who has proven himself as a talented leader, will continue to successfully implement the long-term vision and goals of Swedbank," said Mančinskis.
Rubenis has spent nineteen years working in finance, of which nine were at Swedbank. He has studied at the Stockholm School of Economics and theology at the University of Latvia.
Swedbank is the largest bank in Latvia by number of clients and by volume of assets. It reaped profits of €121m in 2015.