Yoshii (written: 吉井) is a Japanese surname. Notable people with the surname include:

• Hidekatsu Yoshii (吉井 英勝, born 1942), Japanese politician
• Yoshii Isamu (吉井 勇, 1886–1960), Japanese poet and playwright
• Kanae Yoshii (吉井 香奈恵, born 1993), Japanese idol, singer and actress
• Kazuya Yoshii (吉井 和哉, born 1966), Japanese musician
• Kosuke Yoshii (吉井 孝輔, born 1986), Japanese footballer
• Masato Yoshii (吉井 理人, born 1965), Japanese baseball player
• Naoto Yoshii (吉井 直人, born 1987), Japanese footballer
• Rei Yoshii (吉井 怜, born 1982), Japanese actress
• Sayuri Yoshii (吉井 小百合, born 1984), Japanese speed skater

Fictional characters

• Rui Yoshii, minor character in the anime series Soaring Sky! Pretty Cure