Johor Bahru, abbreviated JB, is the capital city of the Malaysian state of Johor. It is the core city of Johor Bahru District, Malaysia's second-largest district by population and economy. Covering an area of 373.18 km², Johor Bahru had a population of 858,118 people in 2020, making it the nation's largest state capital city by population. It is located at the southern end of the Malay Peninsula, bordering the city-state of Singapore.

Johor Bahru is the financial and business centre of southern Malaysia. It is Malaysia's second best-performing city behind only Kuala Lumpur, in terms of economic competitiveness, prosperity, and ease of doing business, according to the World Bank. It has the fastest urbanisation growth and internet speed among Malaysian cities. As one of the most visited cities globally, Johor Bahru also has the world's busiest land border crossing, via the Johor-Singapore Causeway, KTM Intercity and the future RTS Link to Singapore. Johor Bahru is served by Senai International Airport and the world's 15th-busiest port, Tanjung Pelepas.

During the reign of Sultan Abu Bakar between 1886 and 1895, the city witnessed modernisation from a fishing village, with the construction of administrative centres, offices, schools, civic and religious buildings, and railways to Woodlands, Singapore. Japanese forces occupied Johor Bahru during the Pacific War. Johor Bahru thus became the post-war cradle of Malay nationalism, forming a major political party, UMNO at the Istana Besar in 1946. Granted city status in 1994, Johor Bahru is currently part of the Johor-Singapore Special Economic Zone and Iskandar Malaysia, the nation's largest special economic zone by investment value.

The present area of Johor Bahru was originally known as Tanjung Puteri, and was a fishing village of the Malays. Temenggong Daeng Ibrahim then renamed Tanjung Puteri to Iskandar Puteri upon his arrival to the area in 1858, after acquiring the territory from Sultan Ali. It was renamed to Johor Bahru by Sultan Abu Bakar following the Temenggong's death. The word "Bah(a)ru" means "new" in Malay; thus, Johor Bahru means "New Johor". Bahru is normally written as "baru" in English (Roman) characters, today, although the word appears in other place names with several English spelling variants, such as in Kota Bharu, Kelantan, and Pekanbaru, Riau (Indonesia). The British preferred to write it as Johore Bahru or Johore Bharu, though the currently-accepted western spelling is Johor Bahru—Johore is only spelt Johor, without the letter "e" at the end of the word, in the Malay language. The city's name is also spelt as Johor Baru or Johor Baharu.

Johor Bahru was once known as Shantou, or "Little Swatow", by the city's Chinese community, as most of the Chinese residents are Teochew whose ancestry can be traced back to Shantou, China; they arrived in the mid-19th century, during the reign of Temenggong Daeng Ibrahim. The city, however, is generally known in Chinese as Xinshan, meaning "New Mountain" (Chinese: 新山; pinyin: Xīnshān), as "mountain" may be used to mean "territory" or "land". The name "New Mountain" distinguished it from "Old Mountain" (Jiushan), once used to refer to Kranji and Sembawang (in Singapore), where the Chinese first cultivated black pepper and gambier on plantations before relocating to new lands in Johor Bahru in 1855.

Due to a dispute between the Malays and the Bugis, the Johor-Riau Sultanate was split in 1819 with the mainland portion of the Johor Sultanate coming under the control of Temenggong Daeng Ibrahim while the Riau-Lingga Sultanate came under the control of the Bugis. The Temenggong intended to create a new administration centre for the Johor Sultanate to create a dynasty under the entity of Temenggong. As the Temenggong already had a close relationship with the British and the British intended to have control over trade activities in Singapore, a treaty was signed between Sultan Ali and Temenggong Ibrahim in Singapore on 10 March 1855. According to the treaty, Ali would be crowned as the Sultan of Johor and receive $5,000 (in Spanish dollars) with an allowance of $500 per month. In return, Ali was required to cede the sovereignty of the territory of Johor (except Kesang of Muar which would be the only territory under his control) to Temenggong Ibrahim. When both sides agreed on Temenggong acquiring the territory, he renamed it Iskandar Puteri and began to administer it from Telok Blangah in Singapore.

As the area was still an undeveloped jungle, Temenggong encouraged the migration of Chinese and Javanese to clear the land and to develop an agricultural economy in Johor. The Chinese planted the area with black pepper and gambier, while the Javanese dug parit (canals) to drain water from the land, build roads and plant coconuts. During this time, a Chinese businessman, pepper and gambier cultivator, Wong Ah Fook arrived; at the same time, the Kangchu and Javanese labour contract systems were introduced by the Chinese and Javanese communities. After Temenggong's death on 31 January 1862, the town was renamed "Johor Bahru" and his position was succeeded by his son, Abu Bakar, with the administration centre in Telok Blangah being moved to the area in 1889.

In the first phase of Abu Bakar's administration, the British only recognised him as a maharaja rather than a sultan. In 1855, the British Colonial Office began to recognise his status as a Sultan after he met Queen Victoria. He managed to regain Kesang territory for Johor after a civil war with the aid of British forces and he boosted the town's infrastructure and agricultural economy. Infrastructure such as the State Mosque and Royal Palace was built with the aid of Wong Ah Fook, who had become a close patron for the Sultan since his migration during the Temenggong reign. As the Johor-British relationship improved, Abu Bakar also set up his administration under a British style and implemented a constitution known as Undang-undang Tubuh Negeri Johor (Johor State Constitution). Although the British had long been advisers for the Sultanate of Johor, the Sultanate never came under direct colonial rule of the British. The direct colonial rule only came into effect when the status of the adviser was elevated to a status similar to that of a Resident in the Federated Malay States (FMS) during the reign of Sultan Ibrahim in 1914.