Monzonite is an igneous intrusive rock, formed by slow cooling of underground magma that has a moderate silica content and is enriched in alkali metal oxides.

Such rocks are classified by their relative percentages of quartz, plagioclase, alkali feldspar, and feldspathoid (the QAPF classification).

[2][4] The plagioclase in monzonite is sodium-rich, ranging from oligoclase to andesine, and is moderately well shaped (subhedral to euhedral).

[6][7] Monzonite can also form in extensional crustal settings[3][8] or by partial melting of lower crust of alkali basalt composition.

[12] Monzonite was originally named after the Monzoni range in Val di Fassa (Trento Province, Italy) where it is abundant.