The zucchetto (/(t)suːˈkɛtoʊ, zuːˈ-/, also UK: /tsʊˈ-/, US: /zʊˈ-/, Italian: [dzukˈketto]; meaning 'small gourd', from zucca 'pumpkin' or more generally 'gourd'; plural in English: zucchettos) or solideo, officially a pileolus, is a small, hemispherical, form-fitting ecclesiastical skullcap worn by clerics of the Catholic Church, the Syriac Orthodox Church, by senior clergy in certain denominations of Lutheranism, Anglicanism, and Methodism.

It is also called a pilus, pilos, pileus, pileolo, subbiretum, submitrale, soli deo, berrettino, calotte or calotta.

The zucchetto originated as the Paleo-Balkanic pileus and is related to the beret (which itself was originally a large zucchetto). The official name of the zucchetto—pileolus—means "small pileus" in Latin. Clerics adopted the style circa the Early Middle Ages or earlier, to keep their heads warm and to insulate the tonsure. The name "zucchetto" derives from its resemblance to half a pumpkin. It is similar to the Jewish kippah or yarmulke, but typically differs in construction, with the zucchetto made of separate joined sections and color-coordinated to clerical status. It is normally used only by clergy and not by ordinary people, which also differs from the kippah. The resemblance between the two types of headgear is often seen as being deliberate but the zucchetto is distinct from and predates the skullcap style of kippah and yarmulke by hundreds of years.

In Catholicism, the modern zucchetto is most commonly made of silk. The design utilises eight gores or triangular panels that are joined at the tips to form a hemispherical skullcap. Jutting from the central tip of the zucchetto is the "stem", known as stirpis or stirpes. It is made of a twisted loop of silk cord and is meant to make handling the zucchetto easier. The stirpes is the primary visual distinction between the zucchetto and the Jewish kippah.

The zucchetto traditionally has a lining of thin white chamois as an insulator; this is also to help keep the shape of the zucchetto. Inside the trim, there is a strip of velvet to ensure a secure and comfortable fit. Most modern zucchetto designs include a cloth lining, and the contemporary trend is using ordinary synthetic cloth with a simple, natural cloth lining.

The color of the zucchetto in Catholicism denotes the office held by the wearer:

Some Franciscans have adopted the practice of wearing a brown zucchetto to match their brown habit.

The most common Lutheran and Anglican design can be similar to the Catholic zucchetto or, far more often, similar to the Jewish kippah. A form of the zucchetto is worn by Anglican bishops and is used approximately like that of the Catholic Church. The Anglican "skullcap" differs from the zucchetto primarily in that it is made of six panels, bears a button at centre of the crown, and is of slightly larger dimensions. The other exception is that instead of the Catholic "church violet", Anglican churches usually (but not always) use purple caps on bishops. ^{[citation needed]}