The Dean of the College of Cardinals is the president of the College of Cardinals in the Roman Catholic Church and as such is always a Cardinal of the Holy Roman Church of the episcopal order. The Dean is not necessarily the longest-serving member of the whole College (who might never become a Cardinal Bishop). It was for centuries customary for the longest-serving of the six cardinal bishops of suburbicarian dioceses to be Dean, and this was in fact required by canon law from 1917 until Pope Paul VI empowered the six bishops to elect him from among their number in 1965. This election (a formality until John Paul II's time) must be confirmed by the Pope. While the Dean (or in his absence or inability the Subdean) presides over the College of Cardinals, he has no power of governance over the other cardinals. Instead he functions as primus inter pares in the college. There is no mandatory retirement age for the position.

It is the Dean's responsibility to summon the conclave to elect a new Pope when the previous one dies or resigns, which he presides over unless he is too old to vote in it. According to Canon 355 (from the Latin Code of Canon Law 1983), if the newly-elected Supreme Pontiff is not already a bishop, it is the right of the Dean to ordain him as such. If the Dean is unable, then the right falls to the Sub-Dean, and then to the senior cardinal of the episcopal order.

According to section 4 of Canon 350, the Cardinal Dean has "the title of the diocese of Ostia, together with that of any other church to which he already has a title." The Cardinal Dean, then, continues to hold the title of his former suburbicarian diocese as well as being titular Bishop of Ostia. This has been the case since 1914, by decree of St. Pius X—previous deans since 1150 had given up their prior suburbicarian see for the joint titles of Ostia and Velletri.

Deans of the Sacred College since the Council of Trent

Each name is followed by years of birth and death, then comma–separated years of cardinalate and deanship. Two recent deans have chosen to retire before dying.

• Rodolfo Pio de Carpi (1500–1564) (1536, 1562)
• Francesco Pisani (1494–1570) (1517, 1564)
• Giovanni Girolamo Morone (1509–1580) (1542, 1570)
• Alessandro Farnese, juniore (1520–1589) (1534, 1580)
• Giovanni Antonio Serbelloni (1519–1591) (1560, 1589)
• Alfonso Gesualdo (died 1603) (1561, 1591)
• Tolomeo Gallio (1526–1607) (1565, 1603)
• Domenico Pinelli (1541–1611) (1585, 1607)
• Francois de Joyeuse (1562–1615) (1583, 1611)
• Antonio Maria Galli (1553–1620) (1586, 1615)
• Antonio Maria Sauli (1541–1623) (1587, 1620)
• Francesco Maria Bourbon del Monte (1549–1626) (1588, 1623)
• Ottavio Bandini (1558–1629) (1596, 1626)
• Giovanni Battista Deti (1576–1630) (1599, 1629)
• Domenico Ginnasi (1550–1639) (1604, 1630)
• Carlo Emmanuele Pio de Savoia , seniore (1585–1641) (1604, 1639)
• Marcello Lante della Rovere (1561–1652) (1606, 1641)
• Giulio Roma (1584–1652) (1621, 1652) served less than 5 months
• Carlo de Medici (1595–1666) (1615, 1652)
• Francesco Barberini , seniore (1597–1679) (1623, 1666)
• Cesare Facchinetti (1680–1683) (1643, 1680)
• Niccolo Albergati–Ludovisi (1608–1687) (1645, 1683)
• Alderano Cibo (1613–1700) (1645, 1687)
• Emmanuel–Theodose de la Tour d'Auvergne de Bouillon (1643–1715) (1669, 1700)
• Nicola Acciaiouli (1630–1719) (1669, 1715)
• Fulvio Astalli (1655–1721) (1686, 1719)
• Sebastiano Antonio Tanara (1650–1724) (1695, 1721)
• Francesco del Giudice (1647–1725) (1690, 1724)
• Fabrizio Paolucci (1651–1726) (1697, 1725)
• Francesco Barberini , juniore (1662–1738) (1690, 1726)
• Pietro Ottoboni (1667–1740) (1689, 1738)
• Tommaso Ruffo (1663–1753) (1706, 1740)
• Pietro Luigi Carafa (1677–1755) (1728, 1753)
• Rainiero d'Elci (1670–1761) (1737, 1756)
• Giuseppe Spinelli (1694–1763) (1735, 1761)
• Carlo Alberto Guidoboni Cavalchini (1683–1774) (1743, 1763)
• Fabrizio Serbelloni (1695–1775) (1753, 1774)
• Giovanni Francesco Albani (1720–1803) (1747, 1775) longest deanship
• Henry Benedict Maria Clement Stuart (1725–1807) (1747, 1803) longest total cardinalate
• Leonardo Antonelli (1730–1811) (1775, 1807)
• Alessandro Mattei (1744–1820) (1779, 1814) vacancy caused by his exile by Napoleon
• Giulio Maria della Somaglia (1744–1830) (1795, 1820)
• Bartolomeo Pacca (1756–1844) (1801, 1830)
• Lodovico Micara (1775–1847) (1824, 1844)
• Vincenzo Macchi (1770–1860) (1826, 1847)
• Mario Mattei (1792–1870) (1832, 1860)
• Costantino Patrizi Naro (1798–1876) (1834, 1870)
• Luigi Amat de San Filippo e Sorso (1796–1878) (1837, 1877)
• Camillo de Pietro (1806–1884) (1853, 1878)
• Carlo Sacconi (1808–1889) (1861, 1884)
• Raffaello Monaco de Valletta (1827–1896) (1868, 1889)
• Luigi Oreglia di Santo Stefano (1828–1913) (1873, 1896)
• Serafino Vannutelli (1834–1915) (1887, 1913)
• Vincenzo Vannutelli (1836–1930) (1889, 1915)
• Gennaro Granito Pignatelli de Belmonte (1851–1948) (1911, 1930)
• Francesco Marchetti-Selvaggiani (1871–1951) (1930, 1948)
• Eugene Gabriel Gervais Laurent Tisserant (1884–1972) (1936, 1951)
• Amleto Giovanni Cicognani (1883–1973) (1958, 1972)
• Luigi Traglia (1895–1977) (1960, 1974)
• Carlo Confalonieri (1893–1986) (1958, 1977)
• Agnelo Rossi (1913–1995) (1965, 1986, retired 1993)
• Bernardin Gantin (born 1922) (1977, 1993, retired 2002)
• Joseph Ratzinger (born 1927) (1977, 2002,elected Pope 2005)
• Angelo Sodano (born 1927) (1991,acting 2005)