AC3 or AC-3 may refer to:

Science and technology[edit]

• Dolby AC-3, Dolby Digital audio codec
• AC-3 algorithm (Arc Consistency Algorithm 3), one of a series of algorithms used for the solution of constraint satisfaction problems
• (35414) 1998 AC3, a minor planet
• AC-3, an IEC utilization category
• Ambedkar Community Computing Center (AC3)

Transportation[edit]

• Comte AC-3, a 1920s Swiss bomber/transport aircraft
• Southern Pacific class AC-3, a class of steam locomotive

Video games[edit]

• Ace Combat 3, part of the Ace Combat series of video games
• Armored Core 3, part of the Armored Core series of video games
• Assassin's Creed III, part of the Assassin's Creed series of video games

Other[edit]

• Apple Campus 3, Apple's third large Silicon Valley campus