His Majesty the Emperor; the Emperor
Respectful title used when referring to the Emperor, especially the Emperor of Japan. The 陛下 part marks the reference as honorific.
天皇陛下は式典でお言葉を述べられた。
His Majesty the Emperor gave an address at the ceremony.
His Majesty the Emperor visited the disaster-stricken area.
The new Emperor ascended the throne.
The ambassador had an audience with the Emperor.
The crowd shouted "Long live the Emperor!"