In the Roman Rite of the Catholic Church, Lutheranism, and Anglicanism, an altar bell (also Mass bell, sacring bell, Sacryn bell, saints' bell, sance-bell, or sanctus bell) is typically a small hand-held bell or set of bells. The primary reason for the use of such bells is to create a "joyful noise to the Lord" as a way to give thanks for the miracle taking place atop the altar.

An ancillary function of the bells is to focus the attention of those attending Mass that a supernatural event is taking place on the altar. These are kept on the credence table or some other convenient location within the chancel.

The tradition of bell ringing during the consecration finds its historical roots in the Latin Mass era, where much of the celebrant's dialogue was uttered in subdued tones. During the Middle Ages, the widespread use of rood screens often obstructed the view for many congregants, necessitating the need for auditory signals to denote significant moments within the Mass. Consequently, the ringing of bells emerged as a practical solution, effectively drawing attention to the solemn act of consecration.

While the original practical motivations for bell ringing may have diminished with time, the practice persists as an integral component of liturgical tradition. Its enduring presence serves a dual purpose: not only does it maintain continuity with historical practices, but it also functions as a subtle yet poignant reminder to worshipers, redirecting their focus towards the sacred altar and reinforcing the sanctity of the momentous proceedings unfolding before them.

"A little before the Consecration, if appropriate, a minister rings a small bell as a signal to the faithful." The usual moment chosen for giving the signal of the approach of the Consecration is when the priest stretches out his hands over the host and the chalice while reciting the epiclesis. Mention of this signal was introduced into the Roman Missal in Pope John XXIII's 1962 revision. Even before 1962, it was common practice to give this signal, although it then "ha[d] no authority".

All pre-1970 editions of the Roman Missal, including that of 1962, prescribe continuous ringing of the altar bell while the priest recites the words of the Sanctus at Low Mass. but, in line with its abolition of a hard and fast distinction between a sung and merely spoken Mass, the 1970 edition makes no mention of that practice.

According to local custom, the server also rings the bell once or three times as the priest elevates the consecrated Host and then the Chalice Pre-1970 editions of the Roman Missal prescribe either a triple or a continuous ringing of the bell at each showing of the consecrated species. Pre-1962 editions also prescribe that the server should first light an elevation candle, to be extinguished only after the priest has consumed the Precious Blood or has given Communion to any others who wish to receive it.

On 10 September 1898, the Congregation of Sacred Rites declared inappropriate the use of a gong instead of the altar bell.