Places

• Sadao (town), a town and the surrounding district, Amphoe Sadao, on the border of Malaysia in the Songkhla Province, southern Thailand

Plants

• Neem, (aka sadao or sdao), a tree in the mahogany family Meliaceae

People

• Sadao Yamanaka, a Japanese film director and writer in the 1930s
• Sadao Munemori, posthumous recipient of the U.S. Army Medal of Honor
• Sadao Araki, a Japanese soldier, member of nobility (Baron), politician, and political philosopher born in Tokyo
• Sadao Watanabe (musician) (ja:渡辺貞夫)
• Sadao Watanabe (artist) (ja:渡辺禎雄)
• Sadao Bekku, Japanese classical composer
• Sadao Fuchigami (渕上 貞雄 Fuchigami Sadao), Japanese politician
• Sadao Sei (清貞雄), Japanese astronomer