铝（Aluminium或Aluminum）是一种化学元素，属于硼族元素，其化学符号是Al，原子序数是13。相对密度是2.70。铝是一种较软的易延展的银白色金属。铝是地壳中第三大丰度的元素（仅次于氧和硅），也是丰度最大的金属，在地球的固体表面中占约8%的质量。铝金属在化学上很活跃，因此除非在极其特殊的氧化还原环境下，一般很难找到游离态的金属铝。被发现的含铝的矿物超过270种。最主要的含铝矿石是铝土矿。

铝因其低密度以及耐腐蚀（由于钝化现象）而受到重视。利用铝及其合金制造的结构件不仅在航空航太工业中非常关键，在交通和结构材料领域也非常重要。最有用的铝化合物是它的氧化物和硫酸盐。

Aluminium (in Commonwealth English) or aluminum (in American English) is a chemical element in the boron group with symbol Al and atomic number 13. It is a silvery-white, soft, nonmagnetic, ductile metal. Aluminium is the third most abundant element in the Earth's crust (after oxygen and silicon) and its most abundant metal. Aluminium makes up about 8% of the crust by mass, though it is less common in the mantle below. Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals. The chief ore of aluminium is bauxite.