|Centuries:||1st century – 2nd century – 3rd century|
|Decades:||140s 150s 160s – 170s – 180s 190s 200s|
|Years:||169 170 171 – 172 – 173 174 175|
|172 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||925|
|Bahá'í calendar||−1672 – −1671|
|English Regnal year||N/A|
|Chinese calendar||辛亥年 (Metal Pig)
2868 or 2808
— to —
壬子年 (Water Rat)
2869 or 2809
|Coptic calendar||−112 – −111|
|- Vikram Samvat||228–229|
|- Shaka Samvat||94–95|
|- Kali Yuga||3273–3274|
|Igbo calendar||−828 – −827|
|Iranian calendar||450 BP – 449 BP|
|Islamic calendar||464 BH – 463 BH|
|Minguo calendar||1740 before ROC
|Thai solar calendar||715|
|Wikimedia Commons has media related to 172.|
Year 172 (CLXXII) was a leap year starting on Tuesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Scipio and Maximus (or, less frequently, year 925 Ab urbe condita). The denomination 172 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 Marcus Aurelius crosses the Danube with an expeditionary force, he subdues the Marcomanni and their allies. In a pact signed with the Germanic tribes, he imports them into occupy areas of the Roman Empire that had been depopulated by the plague.
- The Sarmatians attack the lower Danube frontier.
- Miracle in Moravia: As the Roman army is encircled by the Quadi under intense heat, a violent thunderstorm sweeps away the Quadi in a torrent of water and mud, and refreshes the parched legionaries.
- Avidius Cassius, governor of Syria, suppresses an agrarian revolt in Egypt and is made supreme commander of the Roman army in the East.
- Last (5th) year of Jianning era and start of Xiping era of the Chinese Han Dynasty.
- Tatian produces his Diatessaron, a harmony of the four gospels.
- Montanism spreads through the Roman Empire.
- Ke Bineng, Xianbei chieftain (d. 235)
- Lu Su, advisor for the Kingdom of Wu (d. 217)
- Philostratus II the Athenian, Greek sophist (approximate date) (d. c. 250)
- Zang Ba, general of Tao Qian, Lü Bu, and Cao Cao (d. c. 230/240)