An ecclesiastical ring is a finger ring worn by a clergyman, such as a Bishop's ring.
Episcopal rings 
Episcopal rings of the bishops and archbishops 
The bishop, named by the pope but consecrated by his immediate superior cardinal or archbishop, is privileged to wear the ring that is awarded to him by the cardinal. He is then free to obtain and wear his own episcopal rings. The style of the episcopal ring has almost always been very large, gold, stone-set ring.
Aside from the rings a bishop purchases or is given by others, his rings belong to the Church; he will have inherited the previous bishop's ring collection, which is held in trust. While all hierarchs are accorded the honor of being buried wearing a ring, all rings beloning to the Church will be returned to the Church upon the retirement or death of any hierarch.
In a Decree of Pope Boniface IV (A.D. 610) it describes monks raised to the episcopal dignity as anulo pontificali subarrhatis, while at the Fourth Council of Toledo, in 633, it was stated that if a bishop has been deposed from his office and afterwards reinstated, he is to receive back stole, ring and crosier (orarium, anulum et baculum).
St. Isidore of Seville at about the same period couples the ring with the crosier and declares that the former is conferred as "an emblem of the pontifical dignity or of the sealing of secrets". The ring is strictly speaking an episcopal ornament conferred in the rite of consecration, and that it was commonly regarded as emblematic of the mystical betrothal of the bishop to his church.
In the eighth and ninth centuries in manuscripts of the Gregorian Sacramentary and in a few early Pontificals (e.g., that attributed to Archbishop Egbert of York) we meet with various formulae for the delivery of the ring. The Gregorian form, which survives in substance to the present, runs in these terms: "Receive the ring, that is to say, the seal of faith, whereby thou, being thyself adorned with spotless faith, mayst keep unsullied the troth which thou hast pledged to the spouse of God, His Holy Church."
Royal as well as religious seals (signet ring), indicative of discretion and conjugal fidelity, dominate the symbolism of the ring. In the case of bishops, "...a bishop deserting the Church to which he was consecrated and transferring himself to another is to be held guilty of adultery, and is to be visited with the same penalties as a man who, forsaking his own wife, goes to live with another woman." Perhaps this idea of espousals helped to establish the rule, mentioned first in the ninth century, that the episcopal ring was to be placed on the fourth finger ("the ring finger", viz., that next to the little finger) of the right hand. Just as likely, the tradition of using the ring finger of the right hand came about as a result of the prelates having to remove their rings from their index fingers and transferring them to the third finger, as a symbol of humilty and respect for the Eucharist.
Since episcopal rings had to be worn on ceremonial occasions on the outside of the pontifical glove and prelates' gloves, it is common to find medieval specimens extremely large in size and disproportionately heavy. The inconvenience of the looseness was corrected by placing another smaller ring just above it as a ring guard. It was quite common for bishops and popes to wear other rings along with the episcopal ring; the 1882 edition of Caeremoniale episcoporum (Book II, viii, nn. 10-11) still assumed that this was likely to be the case. Today this action is nearly always forbidden, since the hierarchy is privileged to wear only one ring at a time.
Custom prescribed that a layman or a cleric of inferior grade on being presented to a bishop should kiss his hand (called baciamano in Italian), which is to say, an obligation to kiss the episcopal ring. Before the promulgation of the new Enchiridion an indulgence of 50 days resulted from this act. It is still arguable that an indulgence may be received if the ring is considered an object of piety, as kissing an object of piety carries a partial indulgence.
Episcopal rings, both at an earlier and later period, were sometimes used as receptacles for relics. Traditionally, three rings were bestowed: the 'pontifical', the gemmed, and the 'ordinary'. In recent decades, most bishops have only received one ring for the sake of reducing costs. Cardinals have also suffered a reduction in the number of rings they own.
Modern rings for bishops have tended to be far simpler than those of earlier periods: many bishops today choose or are given as gifts wide gold bands with a table showing Christian symbols (a cross, chi-rho, or crucifixion scene, for example), rather than a jeweled ring. The preference and the ring awarded to bishops still tend to be large gold rings adorned by a large central stone. It is understood in modern times that the ring-wearing hierarch is privileged to wear such a ring, since such a ring is forbidden to lesser clergy. In fact it is often the case that a prelate will give an episcopal ring as a private, secret gift to a priest, in hopes that the priest will eventually be elevated in position. This is a completely private gesture of friendship and patronage.
Cardinalatial episcopal rings 
The cardinals' rings (and the ring worn by the pope) are ecclesiastical episcopal rings.
The pope elevates the newly created cardinal when he places the cardinalatial ring on the cardinal's finger. This is a gift from the pope to the new cardinal. Most cardinals keep only this ring, obtaining no other. The style of this ring is the pope's decision and he may choose any design he wishes. The solid gold cardinal's ring chosen by John Paul II is the oblong crucifixion scene. These continue to be worn, but the design was approved by John Paul II; any future pope may choose another design.
Episcopal ring of the papacy 
The most famous ecclesiastical ring in Christendom is the episcopal ring of the pope, known as the "Ring of the Fisherman", the Annulus Piscatoris, a.k.a. "The Fisherman's Ring", a.k.a. "The Ring of St. Peter". Originally intended as the pope's episcopal ring as the Bishop of Rome, it has since become a symbol of global as well as religious power. The origin of the ring design is inspired by Jesus telling St. Peter, who was by trade a fisherman, "I will make you a fisher of men."
The Ring of the Fisherman is represented by a large gold ring with a round or, more recently, an ovaloid, bezel. As recently as the 1970s, it was a large medallion shape. On the face appears the image of St. Peter in a fishing boat on the water; above him is the chosen name of the pope. This is the ring that is broken upon the death or resignation of a pope. A new one is then engraved for the new pope.
The pope's ring is not to be confused with the papal seal, which is what the pope uses to seal documents. The Fisherman's Ring is no longer used to seal anything. Though Pope Benedict XVI chose to wear it at all times, it had not been seen being publicly worn by a pope since the papacy of Pope Pius XII, who refrained from wearing it once his election ceremonies had been concluded.
A collection of rings belonging to the popes of the past is exhibited in a glass case in a room within the papal apartments. The collection is loaned out occasionally, either to museums or religious institutions.
Besides bishops, certain other ecclesiastics are privileged to wear rings. In Roman Catholicism, the privilege to wear a ring indicates the papal recognition and granting of authority to wear such a ring.
Cardinals' rings tend to be as large and flashy as a pope's ring. Prior to the reign of Pope John XXIII, a cardinal was not required to be a bishop, but he would wear a ring even if he had not been consecrated to the episcopate. The cardinal's ring is conferred by the pope himself in the consistory, in which the new cardinal is named to a particular "title", which is to say, in the title of a particular saint and at the level of either a cardinal priest or cardinal bishop. In the past, a cardinal's ring was usually set with a sapphire, while it bore on the inner side of the bezel the arms of the pope conferring it. Modern cardinals' rings are gold with a scene of the crucifixion of Jesus worked in metal, and without a jewel, at the instigation of Pope John Paul II. Cardinals may prefer to wear a ring of their choice as they are privileged to do so. The privilege of wearing a ring has belonged to cardinal-priests at least since the time of Innocent III
Abbots (monastical prelates) in the earlier Middle Ages were permitted to wear rings only by special privilege. A letter of Peter of Blois from the twelfth century shows that at that date the wearing of a ring by an abbot was apt to be considered ostentatious. However, in the later Pontificals, the blessing and delivery of a ring formed part of the ordinary ritual for the blessing of an abbot, and this is still the case. Certain abbesses have received and assumed the privilege of wearing a ring of office.
Such rings cannot ordinarily be worn by these minor prelates during the celebration of Mass. The only exception to this rule is applied to the order of Clerks Regular of St. Viator. They are permitted, by Papal Indult, to wear the ring of investiture even during the Liturgy of the Eucharist.
In the Order of Preachers, commonly known as the Dominican Order, the honorary title of Master of Sacred Theology, roughly equal to an honorary doctorate in theology, includes the privilege of wearing, in non-liturgical ceremonies, a ring, which may be set with an Amethyst. It is not unusual for the ring to be inscribed inside the band with the initials of the previous Masters of Sacred Theology of the province.
The tradition of plain wedding bands worn by certain women religious and conferred upon them in the course of their solemn profession, according to the ritual provided in the Roman Pontifical is found in ancient tradition. Saint Ambrose of Milan speaks as though it were customary for virgins consecrated to God to wear a ring in memory of their betrothal to their heavenly Spouse. This delivery of a ring to professed nuns is also mentioned by several medieval Pontificals, from the twelfth century onwards.
For the year of his office the Moderator of the General Assembly of the Church of Scotland (chairman of the General Assembly) wears an amethyst and gold ring. The stone has incised on it the crest of the Church of Scotland - a burning bush - and around it the words "Nec Tamen Consumebatur" ("Burning but not being consumed"). The words refer to Moses' encounter with the burning bush in the desert. Each year as the retiring Moderator installs his successor in office, he places the ring on the new Moderator's finger.
Modern episcopal rings have a special sliding-band inner mechanism that allows them to be sized and locked into place, eliminating the need to have rings sized or resized. Most Reverend Ludovic Taurin-Cahagne, Bishop of Adramythe in Ethiopia, Apostolic Vicar of the Gallas, ca. 1875, had a unique, lovely ring that locked/unlocked, apparently an early form of adjustability (and perhaps a security mechanism).
For example: "[Cardinal O'Malley said] the [cardinalatial] ring [in the design approved by Pope John Paul II] was open in the back [by a clever sliding-band mechanism], and could be resized at home. That was a bit of a relief, he said, recalling the time he [removed his] bishop's ring during Mass to wash his hands, gave it to a seminarian, and the seminarian decided to see what it felt like to wear a bishop's ring, and the ring got stuck on the seminarian's finger!"
There are times when a bishop may be awarded an episcopal ring with a form of a coat of arms or specific Catholic symbol, such as the ring given to Bp. Henessy of Boston.
Other Christian rings 
Wedding rings, or more strictly, rings given in the betrothal ceremony, were common among Christians under the Roman Empire from an early period. The use of such rings was of older date than Christianity, and there is not much to suggest that the giving of the ring was at first incorporated in any ritual for laypeople, or invested with any precise religious significance. It is known from archeological finds that the betrothal/wedding ring was adorned with Christian emblems. Certain specimens prove this today, such as a gold ring found near Arles, from circa the fourth or fifth century A.D., and bearing the inscription Tecla vivat Deo cum marito seo [suo].
In the coronation ceremony too, it has long been the custom to deliver both to the Sovereign and to the queen consort a ring previously blessed. Perhaps the earliest example of the use of such a ring is in the case of Judith, the stepmother of king Alfred the Great, but it is unclear whether that ring was bestowed upon the queen in virtue of her dignity as queen consort or of her nuptials to King Æthelwulf of Wessex.
Other religious rings:
- At an early date the small keys which contained filings from the chains of St. Peter were welded to a band of metal and worn upon the finger as reliquaries.
- An ancient custom to this day at the Monastery of St. Catherine on Mount Sinai, is to place a ring on the finger of St. Catherine of Alexandria and then wear it as a eulogia (blessing).
- In modern times, rings with ten small knobs or protuberances are common. These are used for reciting the rosary (called a "rosary ring"). The rosary ring was invented during World War I for soldiers in the field to be able to recite the rosary more easily.
- Orthodox Christians have komboskini ("prayer rope") rings with ten knots.
- The little-known but once common memorial ring may be bequeathed to beneficiaries by a deceased loved one. It is usually a plain band of some type, meant to remind the wearers of the deceased. This custom has generally come to an end, but something like it survives today among closely knit, religious families and friends.
- Religious medals are commonly shaped and formed into rings for daily wear and even for devotions. Most common among these is a ring made from a medal of the Archangel Michael, known as "the ring of St. Michael".
- Late in the Roman Christian Era, cameos of saints were often worn by wealthy Christians. Early in the era, simple iron bands were worn by all the faithful, though the wealthy of Rome would often cover their gold rings with charcoal, in order to appear more pious.
- The Claddagh ring is viewed as a religious ring in Ireland, though it symbolises civil status: whether single, engaged or married. However, it does not bear any religious image or symbol.
- McCarthy, James. Rings Through the Ages. 1945.
- Isidore of Seville, P.L., LXXXIII, 783.
- Du Saussay, Panoplia episcopalis, 250.
- See Lacy, Exeter Pontifical, 3.
- McCloud, Henry (1948). Clerical Dress and Insignia of the Roman Catholic Church. The Bruce Publishing Company, Milwaukee.
- Kunz, George. Rings For the Finger. Nabu Press, 2010 ed., copyright 1911.
- "Vatican sends clear message that Pope Benedict XVI will not cast papal shadow after retirement". Washington Post. Associated Press. February 12, 2013. Retrieved February 12, 2013. "The papal ring will be destroyed, along with other powerful emblems of authority, just as they are after a pope’s death."
- Chiron, Yves. Pope Pius IX: The Man and the Myth. Angelus, 2005.
- Jones, William. Rings for the Finger. Chatto & Windus, 1890.
- See Sägmüller, Stetigkeit und Stellung der Cardinale, 163.
- Peter of Blois, P.L., CCVII, 283
- Barbier de Montault, Le costume et les usages ecclesiastiques selon la tradition romaine (Paris, 1897-1901), I, 170.
- Ambrose of Milan, P.L., XVII, 701, 735
- This article incorporates text from a publication now in the public domain: Herbermann, Charles, ed. (1913). Catholic Encyclopedia. Robert Appleton Company. Rings
- Baciamano kissing the episcopal ring (commentary and photos)