O A e o Z (also known as A e o Z, or "A" e o "Z", Portuguese: The A and the Z) is an album by Brazilian rock band Os Mutantes.

It was their first record without founding member Rita Lee, and marked a shift in their sound to progressive rock.

Recorded in 1973, but shelved until 1992, this was Arnaldo Baptista's last studio record with the group.

All tracks are written by Arnaldo Baptista, Sérgio Dias, Liminha and Dinho Leme