Kappa (upper case Κ, lower case κ) is the tenth letter of the Greek alphabet. In the system of Greek numerals it has a value of 20.

In mathematics, the kappa curve is named after this letter; the tangents of this curve were first calculated by Barrow (17th Century).

The upper-case letter Κ is used as a symbol for:

• In textual criticism, the Byzantine text-type (from Κοινη, Koine, the common text).