Simple Summary In the present paper, we report a new genus and species of sap beetles (family Nitidulidae), Protonitidula neli gen. et sp. nov., that was recovered from mid-Cretaceous amber in northern Myanmar, from some 99 million years ago. Protonitidula neli possesses morphological characteristics of both Kateretidae and Nitidulidae. Based on the characteristic broad prosternal process, Protonitidula is tentatively placed in Nitidulidae. Our discovery enriches the fossil record of the family in the Cretaceous Burmese amber. Nitidulidae is the most diverse family of the recently recognized superfamily Nitiduliodea, but Mesozoic nitidulids that are critical for understanding their early diversification are sparse. Here, we report a new genus and species of Nitidulidae, Protonitidula neli gen. et sp. nov., that was recovered from mid-Cretaceous amber in northern Myanmar. The new genus is distinguished from all members of the extant nitidulid subfamilies most prominently by the loose antennal club and the absence of subantennal grooves. Protonitidula neli can be excluded from the closely related Kateretidae and classified into Nitidulidae by the broad and apically expanded prosternal process, although it has many pleisiomorphic characters.