Which orbitals form a pi bond?

p and d orbitals

Explanation:

A π bond forms when two orbitals overlap side-on.

The most common types are formed by the overlap of p orbitals (Fig. 1).

However, d orbitals can also overlap sideways with each other to form dπ-dπ bonds and with p orbitals to form dπ-pπ bonds (Fig. 2).