Crochet thread is specially formulated thread usually made from mercerized cotton for crafting decorative crochet items such as doilies or filet crochet. Crochet thread produces fabric of fine gauge that may be stiffened with starch.

Crochet thread is almost always produced from cotton and has a denser pile and smaller diameter than ordinary yarn. Most crochet threads are thicker in diameter than sewing yarn. Crochet thread can withstand considerable stresses from pulls with sharp hooks.

Crochet manufacturing conventions treat thread and yarn quite differently: manufacturers designate different sizing scales for thread and yarn. Thread is generally packaged on spools instead of skeins or hanks and is offered for sale in a separate section from ordinary yarns or threads. Crochet hooks for use with thread are also sized according to a different scale from yarn hooks. Thread hooks are also manufactured differently from yarn hooks: modern yarn hooks are usually aluminum or plastic, while thread hooks are made of steel and have smaller hook heads and shorter shanks.