Selenoyl fluoride, selenoyl difluoride, selenium oxyfluoride, or selenium dioxydifluoride is a chemical compound with the formula SeO<sub>2</sub>F<sub>2</sub>.
The shape of the molecule is a distorted tetrahedron with the O-Se-O angle being 126.2ð, the O-Se-F angle being 108.0ð and F-Se-F being 94.1ð. The Se-F bond length is 1.685 àand the selenium to oxygen bond is 1.575 àlong.
Selenoyl fluoride can be formed by the action of warm fluorosulfonic acid on barium selenate or selenic acid. SeO<sub>3</sub> + SeF<sub>4</sub> can give this gas along with other oxyfluorides.
Selenoyl fluoride is more reactive than its analogon sulfuryl fluoride. It is easier to hydrolyse and to reduce. It may react violently upon contact with ammonia.
Selenoyl fluoride reacting with xenon difluoride gives FXeOSeF<sub>5</sub>.