In music, tonicization is the treatment of a pitch other than the overall tonic as a tonic for a part of a composition. Tonicization may be achieved through the use of leading tones, dominant-tonic chord progressions, or a combination thereof.

The dominant in the tonicizing progression is referred to as a secondary dominant or V/x, V of x, where x is the tonicized scale degree. The V may be replaced with a vii^o chord (which may be considered a V7 without the root).

Tonicization is an example of tonal chromaticism. Longer tonicizations are considered modulations.