Simple Summary Flowers are beautiful due to their perianth which is frequently colourful and conspicuous. The existence of the colourful perianth is closely related to insect pollination in extant angiosperms. The Early Cretaceous (1.25 million years ago) Yixian Formation in Northeastern China is famous for its great diversity of reproductive organs of early angiosperms. However, unlike typical flowers in extant angiosperms, the previously documented fossil flowers are "naked", namely, they do not have typical perianth, suggestive of a strategy different than the extant one adopted in the reproduction of early angiosperms. However, without fossil evidence, whether there is perianth and whether androecium and gynoecium are protected in early flowers are open questions. In this paper, we document the first flower bud fossil, Archaebuda lingyuanensis, from the Yixian Formation. Besides being the first recorded flower bud (which is fragile and unlikely to be fossilized) in the Early Cretaceous, the flower bud does protect its internal parts, which are vulnerable to various attacks and harm, using the perianth. In addition, perianth plays an important role in attracting insects for successful pollination of early angiosperms. This knowledge on the reproduction of early angiosperms is otherwise unavailable if only the previous fossils are taken into consideration. Background: Although various angiosperms (including their flowers) have been reported from the Yixian Formation (Lower Cretaceous) of China, which is famous worldwide for its fossils of early angiosperms, no flower bud has hitherto been seen in the Early Cretaceous. Such a lack of examples hinders our understanding of the evolution of flowers. Methods: The specimen studied in the present paper was collected from an outcrop of the Yixian Formation (the Barremian-Aptian, Lower Cretaceous) of Dawangzhangzi in Lingyuan, Liaoning, China. The specimen was photographed using a Nikon D200 digital camera, its details were observed and photographed using a Nikon SMZ1500 stereomicroscope, and some of its details were observed using a Leo 1530 VP SEM. Results: We report a fossilized flower bud, Archaebuda lingyuanensis gen. et sp. nov, from the Yixian Formation of China. The debut of Archaebuda in the Yixian Formation provides first-hand material for debate on the early evolution of angiosperm flowers and underscores the great diversity of angiosperms in the Yixian Formation.