ABSTRAK Telah dilakukan penelitian dengan judul Keanekaragaman Vegetasi Pantai di Wilayah Pesisir Kabupaten Aceh Besar, Provinsi Aceh. Penelitian ini dilakukan pada bulan September 2012 sampai dengan bulan Februari 2013. Tujuan penelitian ini adalah untuk mengetahui keanekaragaman jenis tumbuhan pesisir laut yang tumbuh di sepanjang kawasan pesisir laut Kabupaten Aceh Besar. Pengambilan data dilakukan pada 6 lokasi, yakni Amat Aramanyang, Ujong Pancu, Lampuuk, Lhokseudu, Pulo Nasi dan Pulo Breuh. Metode yang digunakan pada penelitian ini adalah Metode Transek Kuadrat. Jumlah total spesies yang ditemukan sebanyak 18 spesies dari tiga kategori vegetasi pantai. Kategori mangrove sejati ditemukan 5 spesies, kategori mangrove ikutan sebanyak 8 spesies dan kategori vegetasi non-mangrove ditemukan sebanyak 5 spesies. Hasil penelitian dari keenam stasiun penelitian menunjukan bahwa tingkat keanekaragaman pada keenam stasiun penelitian begitu rendah dengan kisaran nilai dibawah angka satu. Nilai tersebut dikategorikan sangat rendah bila dilihat indeks nilai kategori berdasarkan Shannon & Wienner, yang jika H' < 1, maka keanekaragaman tersebut dikategorikan rendah. Kata kunci : Vegetasi pantai, Mangrove, Keanekaragaman, Aceh Besar. ABSTRACT The research about Vegetation Diversity in Coastal Region of Aceh Besar, Province of Aceh. This study was conducted from September 2012 to February 2013. The purpose of this study was to determined diversity of coastal plant species growing along the coastal areas of Aceh Besar district. Data were collected at 6 locations, they were Amat Aramanyang, Ujong Pancu, Lampuuk, Lhokseudu, Pulo Nasi, and Pulo Breuh. The method used in this study was a square transect method. Total of species were found 18 species of three categories of coastal vegetation. Category of true mangrove was found 5 species, imitated mangrove 8 species, and non – mangrove 5 species. The results of the study showed that the six stations on the sixth level of diversity research station were so low with the range of values number below. That values were categorized very low if they were viewed index value category by Shannon & Wienner, if H ' < 1, so it was low diversity categorized. Keywords : Coastal Vegetation, Mangrove, Diversity, Aceh Besar.