AbstrakHutan mangrove merupakan formasi hutan yang tumbuh dan berkembang pada daerah landai di muara sungai dan pesisir pantai yang dipengaruhi oleh pasang surut air laut dan pantai berlumpur. Penelitian ini bertujuan untuk menganalisis biodiversitas mangrove di Pulau Mansuar Kabupaten Raja Ampat, Provinsi Papua Barat. Metode yang digunakan yaitu transek kuadrat. Hasil penelitian ditemukan sebanyak 6 famili 11 spesies dan 554 individu mangrove. Komposisi individu tertinggi dimiliki oleh spesies Rhizophora apiculata, sedangkan terendah yaitu spesies Xylocarpus rumpii. Indeks keanekaragaman, kekayaan, dan kelimpahan spesies mangrove pada semua tingkat pertumbuhan tertinggi pada stasiun 3, sedangkan terendah pada stasiun 1. Berdasarkan besaran kriteria yang dikemukakan oleh Shannon-Weiner maka indeks keanekaragaman mangrove di Pantai Yenbubua, Kepulauan Mansuar tergolong kategori sedang. Kata kunci: biodiversitas, kekayaan spesies, Pulau Mansuar, Rhizophora apiculata. AbstractMangrove forests are forest formations that grow and flourish in slopes at the mouth of the rivers and coastal areas that are affected by tidal sea water and muddy beaches. This study aimed to analyze the biodiversity of mangroves in Mansuar Island, Raja Ampat District, West Papua Province. The method used was quadrat transects. The results of the study showed that there were 6 families of 11 species and 554 individuals. The highest composition of the individual mangrove species was Rhizophora apiculata, while the lowest composition was Xylocarpus rumpii. The highest diversity index, richness, and abudance spesies in a various growth rate were observed in the station 3, while these lowest parameters were found in the station 1. Based on the magnitude of the criteria proposed by Shannon-Weiner, the index of mangrove diversity in Yenbubua Beach, Mansuar Islands was classified as medium category.