"Harry B. Harris Jr. of Florida, to be Ambassador Extraordinary and Plenipotentiary of the United States of America to the Republic of Korea," the release said on Friday.
Trump initially selected Harris to serve as US ambassador to Australia, but changed his mind in April amid developments on the Korean Peninsula.
Harris, who currently resides in the US state of Hawaii, served in every geographic combatant command region and he has held seven command tasks, the release noted.
As Trump continues to prepare for a summit with North Korean leader Kim Jong Un on June 12 in Singapore, filling the ambassador to South Korea post remains a crucial task, according to the release.