304 may refer to:

• The year 304 or the year 304 BC.
• Area code 304, in West Virginia
• 304 (number), the natural number
• 304 (card game), a card game popular in Sri Lanka and Tamil Nadu
• 304 Olga, a main-belt asteroid
• Peugeot 304, a small family car
• SAE 304 stainless steel, the most common type of stainless steel,
• HTTP 304
• 304, a fictional class battlecruiser in the Stargate series.
• 0304 (with intentional leading zero), an album by Jewel
• a "304 woman", a slang term meaning a promiscuous woman—when 304 is typed into a hand-held calculator, then turned upside down, the symbols resemble the word "hoe".