In mathematics, the term ideal has multiple meanings.

• ideals are special subsets of a ring considered in abstract algebra.
• ideals appear in order theory and are a special kind of lower sets of an order.

In physics, ideal may refer to

• The ideal gas law which governs the pressure of an ideal gas
• An ideal transformer, a transformer having zero resistance and perfect magnetic threading
• A thought experiment, sometimes called an ideal experiment

Ideal is also the name of a late 1990s/early 2000s American R&B singing group.