Year 884 (DCCCLXXXIV) was a leap year starting on Wednesday (link will display the full calendar) of the Julian calendar.

• March 1 – Diego Rodríguez Porcelos, count of Castile, founds and repopulates (repoblación) Burgos and Ubierna (Northern Spain), under the mandate of King Alfonso III of Asturias.^[1]
• Summer – King Carloman II reverts to the former fall-back of 'pay and pray', buying (with Danegeld) a truce at Amiens, while he raises 12,000 lbs of silver for the Vikings to depart.
• December 12 – Carloman II dies after a hunting accident. He is succeeded by his cousin, Emperor Charles the Fat, who for the last time reunites the Frankish Empire.

• King Æthelred II of Mercia marries Princess Æthelflæd, daughter of King Alfred the Great. He accepts Wessex overlordship, and demotes himself to become "Lord of the Mercians".

• January 6 – Hasan ibn Zayd, founder of the Zaydid Dynasty, dies after a 20-year reign at Amul. He is succeeded by his brother Muhammad, as emir of Tabaristan.
• May 10 – Ahmad ibn Tulun, founder of the Tulunid Dynasty, dies after a 15-year reign. He is succeeded by his son Khumarawayh, as ruler of Egypt and Syria.
• Fall – The Arabs sack the abbey of Monte Cassino in two raids (September and November). The bulk of the monastic community flee to Teano (Campania).

• March 4 – Emperor Yōzei is forced to abdicate the throne by Fujiwara no Mototsune, chancellor (kampaku) of the Japanese royal court. He is succeeded by his great-uncle Kōkō.
• The Huang Chao rebellion is suppressed by forces of Emperor Xi Zong, with the help of the Shatuo Turks. Chinese warlords rule the country, instead of the imperial government.

• May 15 – Pope Marinus II dies at Rome, after a reign of less than 1½ years. He is succeeded by Adrian III (also referred to as Hadrian III), as the 109th pope of the Catholic Church.

• Burchard II, duke of Swabia (or 883)
• Kong Xun, Chinese general and governor (d. 931)
• Zhang Yanhan, Chinese official and chancellor (d. 941)

• January 6 – Hasan ibn Zayd, Muslim emir of Tabaristan
• May 10 – Ahmad ibn Tulun, Governor of Egypt and founder of the Tulunid dynasty (b. 835)
• May 15 – Marinus I, pope of the Catholic Church
• June 11 – Shi Jingsi, general of the Tang Dynasty
• June 29 – Yang Shili, general of the Tang Dynasty
• July 13 – Huang Chao, Chinese rebel leader (b. 835)
• September – Buran bint al-Hasan ibn Sahl, Abbasid consort (b. 807)^[2]
• October 12 – Tsunesada, Japanese prince (b. 825)
• December 12 – Carloman II, king of the West Frankish Kingdom
• Al-Abbas ibn Ahmad ibn Tulun, Tulunid prince and usurper
• Colcu mac Connacan, Irish abbot and historian
• Dawud al-Zahiri, Muslim scholar (or 883)
• Empress Cao (Huang Chao's wife)
• Domnall mac Muirecáin, king of Leinster
• Li Changyan, Chinese warlord and governor
• Shang Rang, Chinese rebel leader (approximate date)
• Wang Duo, chancellor of the Tang Dynasty
• Zhou Ji, Chinese warlord (approximate date)

• Martínez Díez, Gonzalo (2005). El Condado de Castilla (711-1038). La historia frente a la leyenda (in Spanish). Valladolid: Junta de Castilla y León. ISBN 84-9718-275-8.