Begonia ilinensis is a newly described species of Begonia sect. Baryandra, first found in the coastal areas of Ilin Island, off the southwestern coasts of Mindoro Island in the Philippines. The species resides in exposed to semi-exposed limestone areas on the coast. The species is notable for its dormancy during the dry months, where it is limited to its minute rhizomes. It only starts growing its foliage and flowers during the wet season of June to November. Morphologically, the species is relatively small compared to most Baryandra species in the Philippines, but resembles Begonia luzonensis, a resident of nearby Luzon Island, mainly by its leaf margins. However, the species is much smaller compared to B. luzonensis specifically in terms of lamina, inflorescences, and capsules, and it lacks the characteristic rusty villous indumentum of B. luzonensis on its leaves, peduncles, and petioles. We also documented and mapped other Begonia sect. Baryandra that we have found thriving on the same habitat as B. ilinensis on other portions of the Philippines to shed further insights on the ecology of these coastal Begonias based on their habitat preferences.