Riyadh is the capital and largest city of Saudi Arabia. It is also the capital of the Riyadh Province and the centre of the Riyadh Governorate. Located on the eastern bank of Wadi Hanifa, the current form of the metropolis largely emerged in the 1950s as an offshoot of the 18th century walled town following the dismantling of its defensive fortifications.

It is the largest city on the Arabian Peninsula, and is situated in the center of the Nafud desert, on the eastern part of the Najd plateau. The city sits at an average of 600 meters (2,000 ft) above sea level, and receives around 5 million tourists each year, making it the forty-ninth most visited city in the world and the 6th in the Middle East. Riyadh had a population of 7.0 million people in 2022, making it the most-populous city in Saudi Arabia, 3rd most populous in the Middle East, and the 38th most populous in Asia.

The first mention of the city by the name Riyadh was in 1590, by an Arab chronicler. In 1745, Dahham ibn Dawwas, who was from the neighboring Manfuhah, seized control of the town. Dahham built a mudbrick palace and a wall around the town, and the best-known source of the name Riyadh is from this period, thought to be referring to the earlier oasis towns that predated the wall built by Ibn Dawwas. In 1744, Muhammad ibn Abd al-Wahhab formed an alliance with the Emir of Diriyah, Muhammad bin Saud, and they took Riyadh from Dahham. However their state, now known as the First Saudi state, collapsed in 1818. Turki ibn Abdullah founded the Second Saudi state in the early 19th century and made Riyadh his capital in 1825. However, his reign over the city was disrupted by a joint Ottoman–Rashidi alliance. Finally, in the early 20th century, Ibn Saud, retrieved his ancestral rule in 1902 with the Emirate of Riyadh and consolidated his rule by 1926 with the final Saudi conquest of Hejaz, subsequently naming his kingdom 'Saudi Arabia' in September 1932 with Riyadh as the capital. The town was the administrative center of the government until 1938, when Ibn Saud moved to the Murabba Palace. In the 1950s, the walls were dismantled and Riyadh metropolis outgrew as an offshoot of the walled town.

Riyadh is the political and administrative center of Saudi Arabia. The Consultative Assembly, the Council of Ministers, the king and the Supreme Judicial Council are all situated in the city. Alongside these four bodies that form the core of the legal system of Saudi Arabia, the headquarters of other major and minor governmental bodies are also located in Riyadh. The city hosts 114 foreign embassies, most of which are located in the Diplomatic Quarter in the western reaches of the city.

Riyadh also holds economic significance, as it contains the headquarters of many banks and major companies, such as the Saudi National Bank (SNB), Alrajhi Bank, SABIC, Almarai, stc Group, and Highway 65, known locally as the King Fahd Road, runs through some of these important centers in the city, including the King Abdullah Financial District, one of the world's largest financial districts, the Al-Faisaliah Tower and the Kingdom Center. Riyadh is one of the world's fastest-growing cities in population and is home to many expatriates.

The city is divided into fifteen municipal districts, which are overseen by the Municipality of Riyadh headed by the mayor; and the Royal Commission for Riyadh City, which is chaired by the governor of the province, Faisal bin Bandar. As of July 2020, the mayor is Faisal bin Abdulaziz bin Mohammed bin Ayyaf Al-Muqrin. Riyadh will host Expo 2030, becoming the second Arab city to host after Dubai in 2020.

On the outskirts of Riyadh is Diriyah, the original home of the ruling House of Saud and site of At-Turaif Palace, a UNESCO heritage site.