|Centuries:||6th century – 7th century – 8th century|
|Decades:||640s 650s 660s – 670s – 680s 690s 700s|
|Years:||675 676 677 – 678 – 679 680 681|
|678 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1431|
|Bahá'í calendar||-1166 – -1165|
|English Regnal year||N/A|
|Chinese calendar||丁丑年 (Fire Ox)
3374 or 3314
— to —
戊寅年 (Earth Tiger)
3375 or 3315
|- Vikram Samvat||734–735|
|- Shaka Samvat||600–601|
|- Kali Yuga||3779–3780|
|Igbo calendar||-322 – -321|
|Minguo calendar||1234 before ROC
|Thai solar calendar||1221|
|Wikimedia Commons has media related to 678.|
Year 678 (DCLXXVIII) was a common year starting on Friday (link will display the full calendar) of the Julian calendar. The denomination 678 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.
- The first Arab siege of Constantinople (674–678) ends.
- April 27 – Japanese Emperor Temmu holds divination for the purpose of proceeding to the Abstinence-palace.
- May 3 – When the Japanese Emperor and the officers are about to leave for the Abstinence-palace at the hour of sunrise, Princess Tōchi suddenly takes ill and dies within the Palace. For this reason the Emperor is unable to proceed. No Sacrifice to the Gods of Heaven and Earth results in take place.
- May 10 – Princess Tōchi is buried at a place named Akō. The Emperor, her father, is graciously pleased to raise lament for her.
- June 27 – Pope Agatho succeeds Pope Donus as the 79th pope. He is the first to stop paying tribute to the Byzantine Emperor upon election.
- In Japan, the national worshiping to the Gods of Heaven and Earth is planned, and the Emperor tries to select a woman as a Saiō to make her serve the Gods. However, the plan is not successful because the woman, Princess Tōchi, suddenly dies.
- King Uija of Baekje
- Zhang Wenguan
- May 3 – Princess Tōchi, empress of Japan
- Abdullah ibn Aamir, a Sahaba and Governor of Busra as well as famous Arab General