Tsuboi (written: 坪井, 壺井 or 壷井) is a Japanese surname. Notable people with the surname include:

• Keisuke Tsuboi (坪井 慶介, born 1979), Japanese footballer
• Sakae Tsuboi (壺井 栄, 1899–1967), Japanese writer and poet
• Shigeji Tsuboi (壺井 繁治, 1897–1975), Japanese poet
• Sho Tsuboi (坪井 翔, born 1995), Japanese racing driver
• Tatsuya Tsuboi (壷井 達也, born 2002), Japanese figure skater
• Tomochika Tsuboi (坪井 智哉, born 1974), Japanese baseball player
• Tomohiro Tsuboi (坪井 智浩, born 1971), Japanese voice actor
• Unoko Tsuboi (壷井 宇乃子, born 1917), Japanese swimmer