noun
His Majesty the Emperor; the reigning emperor
Formal term used in official contexts to refer to the current emperor of Japan.
今上天皇は令和の時代を象徴される。
His Majesty the Emperor symbolizes the Reiwa era.
天皇 is the general term for 'emperor', while 今上天皇 specifically refers to the current reigning emperor.
今上 (kinjō, 'present reign') + 天皇 (tennō, 'emperor'). A formal title used for the current emperor.