W3 or W-3 may refer to:

• W3 (tram), a class of electric trams built by the Melbourne & Metropolitan Tramways Board
• W3, a postcode district in the W postcode area
• Apple W3, a wireless chip used in the Apple Watch Series 4.
• PZL W-3 Sokół, a Polish helicopter
• The Amazing 3, a manga and anime series, known in Japan as Wonder 3
• Arik Air, which has IATA code W3
• The fourth step of the W0-W6 scale for the classification of meteorites by weathering
• The U.S. Internal Revenue Service form W-3, a transmittal form for Form W-2 information
• Webster's Third New International Dictionary, the 1961 edition of Webster's Dictionary
• The World Wide Web, abbreviated 'W3' on the earliest web pages
• World Wide Web Consortium, international standards organization for the World Wide Web (abbreviated WWW or W3)
• Windows 3.0, a Microsoft operating system

• Warcraft III: Reign of Chaos, the third game in the Warcraft series.
• Worms & Reinforcements United, a game bundle composing the first Worms game and the Worms Reinforcements expansion pack

• All pages with titles containing w3s
• All pages with titles containing w3
• WWW (disambiguation)
• 3W (disambiguation)
• 3 (disambiguation)
• W (disambiguation)
• Web development tools