A with tilde (majuscule: Ã, minuscule: ã) is a letter of the Latin alphabet formed by addition of the tilde diacritic over the letter A. It is used in Portuguese, Guaraní, Kashubian, Taa, Aromanian, and Vietnamese. In the past, it was also used in Greenlandic.

The name of the letter in the Phoenician period resembled the Hebrew name aleph meaning “ox”; the form is thought to derive from an earlier symbol resembling the head of an ox. The letter was taken over by the Greeks in the form of alpha.

The word 'a' is classified as an indefinite article. This means it doesn't refer to a specific, identifiable entity but rather any member of a group. 'A' is used to introduce a singular noun (or pronoun) when the exact identity of that noun isn't crucial to the meaning of the sentence.

It is similar in shape to the Ancient Greek letter alpha, from which it derives. The uppercase version consists of the two slanting sides of a triangle, crossed in the middle by a horizontal bar. The lowercase version can be written in two forms: the double-storey ⟨a⟩ and single-storey ⟨ɑ⟩.