Si3 may refer to:

• SI3, a diamond clarity guide
• Si3 (film), a 2017 Tamil language film

• Vince Jones
• Vince Jukic
• Vince Karalius
• Vince kennedy mcmahon
• Vince Larkin
• Vince Lateano
• Vince Lester
• Vince Lia
• Vince Locke
• Vince Lovegrove
• Vince Macaulay
• Vince MacLean
• Vince Maloney
• Vince Mangano
• Vince Manuwai
• Vince Marinello
• Vince Martin
• Vince Martin (actor)
• Vince Martino
• Vince Martin (politician)
• Vince Martin (singer)
• Vince Mazza
• Vince McFadden
• Vince mcmahon
• Vince McMahon, Jr.