|Millennium:||1st millennium BC|
|23 BC by topic|
|Gregorian calendar||23 BC|
|Ab urbe condita||731|
|Ancient Greek era||189th Olympiad, year 2|
|Balinese saka calendar||N/A|
|Chinese calendar||丁酉年 (Fire Rooster)|
2674 or 2614
— to —
戊戌年 (Earth Dog)
2675 or 2615
|Coptic calendar||−306 – −305|
|Ethiopian calendar||−30 – −29|
|- Vikram Samvat||34–35|
|- Shaka Samvat||N/A|
|- Kali Yuga||3078–3079|
|Iranian calendar||644 BP – 643 BP|
|Islamic calendar||664 BH – 663 BH|
|Julian calendar||23 BC|
|Minguo calendar||1934 before ROC|
|Seleucid era||289/290 AG|
|Thai solar calendar||520–521|
104 or −277 or −1049
— to —
105 or −276 or −1048
Year 23 BC was either a common year starting on Saturday or Sunday or a leap year starting on Friday, Saturday or Sunday (link will display the full calendar) of the Julian calendar (the sources differ, see leap year error for further information) and a common year starting on Friday of the Proleptic Julian calendar. At the time, it was known as the Year of the Consulship of Augustus and Varro (or, less frequently, year 731 Ab urbe condita). The denomination 23 BC 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.
- Caesar Augustus becomes Roman consul for the eleventh time. His co-consul is Aulus Terentius Varro Murena.
- Augustus relinquishes the position of consul, retains that of tribune of Rome, and assumes that of Princeps, or "First Citizen." (see Roman Empire).
- Augustus gets seriously ill: he gives Agrippa his signet ring and grants him the title imperium pro consule.
- Marcus Claudius Marcellus (nephew of Augustus) falls ill from a fever shortly after his uncle recovers and dies at the age of nineteen while serving as an aedile.
- The Nubians, led by queen Kandake Amanirenas, take the initiative against the Roman Empire, and attack the Roman province of Egypt moving towards Elephantine.
- In response to Meroë's incursions into Upper Egypt, the Roman legions move south and raze Napata. (History of Sudan).
- Herod the Great builds a palace in Jerusalem and the fortress Herodian in Judaea. He also marries his third wife, named Mariamne, the daughter of high priest Simon.
- Following coinage reform, the as is struck in reddish pure copper, instead of bronze. The denominations of sestertius and dupondius are introduced as large bronze coins.
- Ma'nu III Saphul becomes ruler of Osroene.
- The Roman writer, architect and engineer Marcus Vitruvius Pollio finishes writing De Architectura (known today as The Ten Books of Architecture), a treatise in Latin on architecture, and perhaps the first work about this discipline.
- The Roman poet Horace publishes the first three books of Odes.
- Dong Xian, Chinese politician and general (d. 1 BC)
- Herod Archelaus, ethnarch of Samaria (Judea) (d. AD 18)
- Marcus Claudius Marcellus, son of Octavia and nephew of Augustus (b. 42 BC)