Year 723 (DCCXXIII) was a common year starting on Friday of the Julian calendar. The denomination 723 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.

• Gunakamadeva, Lichhavi ruler (rajah), founds the city of Kathmandu (modern Nepal). During his reign, he transforms the agrarian society to an industrial city trading between India and Tibet.^[1]

• Boniface, Anglo-Saxon missionary, fells Thor's Oak (a sacred tree) near Fritzlar in Hesse, marking the decisive event in the Christianization of the northern Germanic tribes (approximate date).
• Boniface makes Büraburg, a fortified Frankish settlement, his temporary religious base.

• Arbeo, bishop of Freising (approximate date)
• Isonokami no Yakatsugu, Japanese nobleman (d. 781)

• October 3 – Elias I of Antioch, Syriac Orthodox Patriarch of Antioch.^[2]
• Adalbert, duke of Alsace
• Fachtna mac Folachtan, Irish abbot
• Ō no Yasumaro, Japanese nobleman