|Centuries:||3rd century – 4th century – 5th century|
|Decades:||290s 300s 310s – 320s – 330s 340s 350s|
|Years:||323 324 325 – 326 – 327 328 329|
|326 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1079|
|Chinese calendar||乙酉年 (Wood Rooster)
3022 or 2962
— to —
丙戌年 (Fire Dog)
3023 or 2963
|- Vikram Samvat||382–383|
|- Shaka Samvat||248–249|
|- Kali Yuga||3427–3428|
|Iranian calendar||296 BP – 295 BP|
|Islamic calendar||305 BH – 304 BH|
|Minguo calendar||1586 before ROC
|Seleucid era||637/638 AG|
|Thai solar calendar||868–869|
Year 326 (CCCXXVI) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Constantinus and Constantinus (or, less frequently, year 1079 Ab urbe condita). The denomination 326 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
- Emperor Constantine the Great travels to Rome to celebrate the 20th anniversary of his accession to power, but while en route at Pola he gives order to execute his older son, Crispus Caesar, possibly on charges of adultery.
- Fausta, second wife of Constantine I, is also executed. She is suffocated in a hot bath.
- Constantine I founds Constantinople and incorporates Byzantium into the new capital. He reorganises the Roman army in smaller units classified into three grades: palatini, (imperial escort armies); comitatenses, (forces based in frontier provinces) and limitanei (auxilia border troops).
- Constantine I promulgates laws against the prostitution of maidservants, and for the humanization of prisons.
- Constantine the Great, from the Basilica of Maxentius and Constantine, Rome, is finished. It is now kept at Palazzo dei Conservatori, Rome.
- September 14 (traditional date) – Helena, mother of Constantine I, discovers the so-called True Cross and the Holy Sepulchre (Jesus's tomb) in Jerusalem. On her pilgrimage, she pauses on the Aegean island of Patros where she is said to found the church of Panagia Ekatontapiliani.
- Helena tells Constantine that he must atone for executing his son and wife by building churches and at about this date construction begins on Old St. Peter's Basilica, the first church on the traditional site of Saint Peter's tomb in Rome, and on the basilica of Golgotha on Calvary outside Jerusalem.
- Probable date – Christianity is introduced to the Kingdom of Iberia (modern-day Georgia) by Saint Nino.
- Constantius Gallus, Caesar and son of Julius Constantius (d. 354)
- Murong Chui, general and founder of Later Yan (d. 396)
- April 17 – Alexander, Patriarch of Alexandria
- Crispus, son of Constantine I (executed)
- Fausta, second wife of Constantine I (executed)
- Empress Liu