Baddeleyite is a rare zirconium oxide mineral (ZrO2) or zirconia. It occurs in a variety of monoclinic prismatic crystals, with colors ranging from colorless to yellow, green, and dark brown.

It was first described in 1892 in Sri lanka and in Minas Gerais and Jacupiranga, São Paulo, Brazil, and named for Joseph Baddeley, who described the occurrences in Sri Lanka.

It has a specific gravity of 5.5 to 6 and a Mohs hardness of 6.5. It is transparent to translucent with a high indices of refraction of n?=2.130, n?=2.190, and n?=2.200. It is a refractory mineral, with a melting point of 2700 °C. Hafnium is a substituting impurity and may be present from 0.1 to several percent.

Baddeleyete is often found as detrital grains in gravels. Its primary occurrence is in high temperature veins and in syenite, carbonatite, kimberlite, and lamproite intrusions. Because of their refractory nature and stability under diverse conditions, baddeleyete grains, along with zircon, are used for uranium-lead radiometric age determinations.