硅酸盐水泥，又称波特兰水泥（英语：Portland Cement），是由硅酸盐水泥熟料、0%-5%石灰石或粒化高炉炉渣、适量石膏磨细制成的水硬性胶凝材料。

硅酸盐水泥熟料的主要成分为硅酸三钙（3CaO·SiO₂）、硅酸二钙（2CaO·SiO₂）、铝酸三钙（3CaO·Al₂O₃）和铁铝酸四钙（4CaO·Al₂O₃·Fe₂O₃）。当与水混合时，发生复杂的物理和化学反应，称为水化（hydrate）。从水泥加水伴和后，成为具有可塑性的水泥浆，到水泥浆逐渐变稠失去塑性但尚未具有强度，这一过程称为“凝结”。随后产生明显的强度并逐渐发展成坚硬的水泥石，这一过程称为硬固（harden）。凝结和硬化是人为划分的，实际上是一个连续的物理化学变化过程。

Portland cement is the most common type of cement in general use around the world, used as a basic ingredient of concrete, mortar, stucco, and most non-speciality grout. It was developed from other types of hydraulic lime in England in the mid 19th century and usually originates from limestone. It is a fine powder produced by heating materials in a kiln to form what is called clinker, grinding the clinker, and adding small amounts of other materials. Several types of Portland cement are available with the most common being called ordinary Portland cement (OPC) which is grey in color, but a white Portland cement is also available.