固相合成是指一类在固体表面上进行的化学合成，本意指有机固相合成，广义的固相合成也包括无机固相合成。无机固相合成一般用来合成有特定晶型的无机晶体。有机固相合成中，采用固相有机高分子作为载体，整个反应均在这个高分子上进行。这类反应通过多步完成，中间形成的产物一直连接在高分子载体之上。反应中的小分子试剂与低分子副产物均能用过滤除去，十分方便。

多肽固相合成是由美国化学家罗伯特·布鲁斯·梅里菲尔德于1963年报道，梅里菲尔德也因此于1984年获得诺贝尔化学奖。当时他仅用8天就合成了过去用液相合成法要花一年才能合成的舒缓激肽。这种方法不但广泛运用于多肽合成，还能用在寡糖、寡核苷酸的合成上，极大的促进了合成化学的发展。

In chemistry, solid-phase synthesis is a method in which molecules are bound on a bead and synthesized step-by-step in a reactant solution; compared with normal synthesis in a liquid state, it is easier to remove excess reactant or byproduct from the product. In this method, building blocks are protected at all reactive functional groups. The two functional groups that are able to participate in the desired reaction between building blocks in the solution and on the bead can be controlled by the order of deprotection. This method is used for the synthesis of peptides, deoxyribonucleic acid (DNA), and other molecules that need to be synthesized in a certain alignment. More recently, this method has also been used in combinatorial chemistry and other synthetic applications. The process was originally developed in the 1950s and 1960s by Robert Bruce Merrifield in order to synthesize peptide chains, and which was the basis for his 1984 Nobel Prize in Chemistry.