Al-Walid ibn Abd al-Malik ibn Marwan (c. 674 – 23 February 715), commonly known as al-Walid I, was the sixth Umayyad caliph, ruling from October 705 until his death in 715. He was the eldest son of his predecessor, Caliph Abd al-Malik (r. 685–705). As a prince, he led annual raids against the Byzantines from 695 to 698 and built or restored fortifications along the Syrian Desert route to Mecca. He became heir apparent in c. 705, after the death of the designated successor, Abd al-Malik's brother Abd al-Aziz ibn Marwan.

Under al-Walid, his father's efforts to centralize government, impose a more Arabic and Islamic character on the state, and expand its borders were continued. He heavily depended on al-Hajjaj ibn Yusuf, his father's powerful viceroy over the eastern half of the caliphate. During his reign, armies commissioned by al-Hajjaj conquered Sind and Transoxiana in the east, while the troops of Musa ibn Nusayr, the governor of Ifriqiya, conquered the Maghreb and Hispania in the west, bringing the caliphate to its largest territorial extent. War spoils from the conquests enabled al-Walid to finance impressive public works, including his greatest architectural achievement, the Great Mosque of Damascus, as well as the al-Aqsa Mosque in Jerusalem, the expansions of the Prophet's Mosque in Medina and the Great Mosque of Sana'a, and the building of the historical city of Anjar. He was the first caliph to institute programs for social welfare, aiding the poor and handicapped among the Muslim Arabs of Syria, who held him in high esteem.

His reign was marked by domestic peace and prosperity and likely represented the peak of Umayyad power, though it is difficult to ascertain his direct role in its affairs. The balance al-Walid maintained among the elites, including the Qays and Yaman army factions, may have been his key personal achievement. On the other hand, the massive military expenditures of his rule, as well as his extravagant grants to the Umayyad princes, became a financial burden on his successors.

Al-Walid was born in Medina in c. 674, during the rule of Mu'awiya I (r. 661–680), the founder and first caliph of the Umayyad Caliphate. His father, Abd al-Malik ibn Marwan, was a member of the Umayyad dynasty. While Mu'awiya belonged to the Umayyads' Sufyanid branch, resident in Syria, al-Walid's family was part of the larger Abu al-As line in the Hejaz (western Arabia, where Mecca and Medina are located). His mother, Wallada bint al-Abbas ibn al-Jaz, was a descendant of Zuhayr ibn Jadhima, a famous 6th-century chief of the Banu Abs tribe. In 684, after Umayyad rule collapsed amid the Second Muslim Civil War, the Umayyads of the Hejaz were expelled by a rival claimant to the caliphate, Ibn al-Zubayr, and relocated to Syria. There al-Walid's grandfather, the elder statesman Marwan I (r. 684–685), was recognized as caliph by pro-Umayyad Arab tribes. With the tribes' support, he restored the dynasty's rule in Syria and Egypt by the end of his reign. Abd al-Malik succeeded Marwan and conquered the rest of the caliphate, namely Iraq, Iran, and Arabia. With the key assistance of his viceroy of Iraq, al-Hajjaj ibn Yusuf, Abd al-Malik instituted several centralization measures, which consolidated Umayyad territorial gains.

The war with the Byzantine Empire, which dated to the Muslim conquest of Syria in the 630s, resumed in 692 after the collapse of the truce that had been reached three years earlier. Annual campaigns were thereafter launched by the Umayyads in the Arab–Byzantine frontier zone and beyond. During his father's caliphate, al-Walid led the campaigns in 696, 697, 698 and 699. In his summer 696 campaign, he raided the area between Malatya (Melitene) and al-Massisa (Mopsuestia), while in the following year, he targeted a place known in Arabic sources as 'Atmar', located at some point north of Malatya. He also led the annual Hajj pilgrimage in Mecca in 698.

In 700 or 701, al-Walid patronized the construction or expansion of Qasr Burqu', a fortified Syrian Desert outpost on the route connecting Palmyra in the north with the Azraq oasis and Wadi Sirhan basin in the south, ultimately leading to Mecca and Medina. His patronage is attested by an inscription naming him as "the emir al-Walid, son of the commander of the faithful". According to the historian Jere L. Bacharach, al-Walid built the nearby site of Jabal Says, likely as a Bedouin summer encampment between his base of operations in al-Qaryatayn and Qasr Burqu'. Bacharach speculates that al-Walid used the sites, located in the territory of Arab tribes, to reaffirm their loyalty, which had been critical to the Umayyads during the civil war.

Toward the end of his reign, Abd al-Malik, supported by al-Hajjaj, attempted to nominate al-Walid as his successor, abrogating the arrangement set by Marwan whereby Abd al-Malik's brother, the governor of Egypt, Abd al-Aziz, was slated to succeed. Though the latter refused to step down from the line of succession, he died in 704 or early 705, removing the principal obstacle to al-Walid's nomination. After the death of Abd al-Malik on 9 October 705, al-Walid acceded. Al-Walid was physically described by the 9th-century historian al-Ya'qubi as "tall and swarthy ... snub-nosed ... with a touch of gray [sic] at the tip of his beard". He noted that al-Walid "spoke ungrammatically". To his father's chagrin, al-Walid abandoned speaking the classical Arabic in which the Qur'an was written but insisted that everyone in his company have knowledge of the Qur'an.

Al-Walid essentially continued his father's policies of centralization and expansion. Unlike Abd al-Malik, al-Walid heavily depended on al-Hajjaj and allowed him free rein over the eastern half of the caliphate. Moreover, al-Hajjaj strongly influenced al-Walid's internal decision-making, with officials often being installed and dismissed upon the viceroy's recommendation.