Januarius (Latin for "devoted to Janus"; ) usually refers to St Januarius, bishop of Benevento or Naples.

Januarius may also refer to:

Months Januarius, the first month of the ancient Roman calendar January, the first month of the modern calendar

People Januarius, the nomen or Roman last name of the gens Januaria Januarius, bishop of Flumenpiscense in Mauretania Januarius of Heraclea, martyred with Felix (Jan. 7) St Januarius of Cordova, martyred with Faustus and Martialis (Oct. 13) St Januarius of Rome: St Januarius ( 10 July 165), son of St Felicity and one of the 7 Holy Brothers, martyr St Januarius the Deacon ( 6 August 258), martyred with Pope Sixtus II and his five other deacons Januarius (), bishop of Lambaese in Roman Numidia Januarius (), bishop of Muzuca St Januarius ( 29 October 298), son of Marcellus, martyred in Spain with his family St Januarius of Zaragoza, sometimes listed among the 18 Martyrs of Zaragoza ( 16 April 303) Januarius ( 24 October 303), martyred with SS Felix, Audactus, Fortunatus, & Septimus St Januarius of Torres ( 304), martyred with SS Gavinus and Protus on Sardinia St Januarius of Nicopolis in Armenia ( ), martyred with St Pelagia Januarius (), bishop of Jericho present at Nicaea Januarius or Januarius II (), bishop of Benevento Januarius I (), bishop of Aquae in Mauretania Januarius (), bishop of Tunusuda Januarius (), bishop of Lamasna Januarius (), bishop of Cunculiana Januarius (), bishop of Aptuca Januarius (), bishop of Centuriona in Numidia Januarius (), bishop of Nara in Byzacene Januarius (), bishop of Libertina Januarius ( 444–447), bishop of Aquileia Januarius (), bishop of Marciana in Lycia Januarius (), bishop of Leontopolis in Lower Egypt Januarius (), bishop of Praeneste Januarius ( ), bishop of Rimini Januarius II (), bishop of Aquae in Mauritania Januarius (), bishop of Centuriae in Numidia Januarius (), bishop of Gauria Januarius (), bishop of Jactera in Numidia Januarius (), bishop of Nasbinca Januarius (), bishop of Tagaste Januarius (), bishop of Valesa Januarius (4th century), founding bishop of Viviers in France Januarius ( 505–515), bishop of Salona in Dalmatia Januarius (), bishop of Vegeselae Januarius (), bishop of Mascula Januarius, bishop of Cagliari on Sardinia & correspondent with Gregory the Great Januarius (), bishop of Malaga Januarius (), bishop of Gattia in Byzacene Januarius (), bishop of Bana in Byzacene Januarius (), bishop of Libertini in Africa Januarius (), bishop of Musti in Africa Prince Januarius, Count of Caltagirone Januarius Gagliano Januarius Kyunosuke Hayasaka Januarius MacGahan Januarius Maria Sarnelli Januarius Zick

See also January, the anglicized form of Januarius Gennaro, the italicized form of Januarius Janus September 19, the Feast of St Januarius Catacombs of St Januarius in Naples Order of St Januarius, bestowed by the titular King of Naples, a member of the Spanish royal family