∆ may refer to:

• Triangle (∆), one of the basic shapes in geometry. Many different mathematical equations include the use of the triangle.
• Delta (letter) (Δ), a Greek letter also used in mathematics and computer science
• Delta baryon (Δ), one of several Baryons consisting of up and down quarks.
• alt-J (Δ), a British indie band
• Laplace operator (Δ), a differential operator
• Increment operator (∆)
• Symmetric difference, in mathematics, the set of elements which are in either of two sets and not in their intersection^[1]

• ᐃ, a letter of Canadian Aboriginal Syllabics
• Latin delta (ẟ), letter of the extended Latin alphabet