A spelling reform is a deliberate, often authoritatively sanctioned or mandated change to spelling rules. Proposals for such reform are fairly common, and over the years, many languages have undergone such reforms. Recent high-profile examples are the German orthography reform of 1996 and the on-off Portuguese spelling reform of 1990, which is still being ratified.

Spelling is a set of conventions for written language regarding how graphemes should correspond to the sounds of spoken language. Spelling is one of the elements of orthography, and highly standardized spelling is a prescriptive element.