Sindh (; Sindhi: سنڌ; Urdu: سندھ, pronounced [sɪndʱ]; historically romanized as Sind) is a province of Pakistan. Located in the southeastern region of the country, Sindh is the third-largest province of Pakistan by land area and the second-largest province by population after Punjab. It is bordered by the Pakistani provinces of Balochistan to the west and north-west and Punjab to the north. It shares an International border with the Indian states of Gujarat and Rajasthan to the east; it is also bounded by the Arabian Sea to the south. Sindh's landscape consists mostly of alluvial plains flanking the Indus River, the Thar Desert in the eastern portion of the province along the international border with India, and the Kirthar Mountains in the western portion of the province.

The economy of Sindh is the second-largest in Pakistan after the province of Punjab; its provincial capital of Karachi is the most populous city in the country as well as its main financial hub. Sindh is home to a large portion of Pakistan's industrial sector and contains two of the country's busiest commercial seaports: Port Qasim and the Port of Karachi. The remainder of Sindh consists of an agriculture-based economy and produces fruits, consumer items and vegetables for other parts of the country.

Sindh is sometimes referred to as the Bab-ul Islam (transl. 'Gateway of Islam'), as it was one of the first regions of the Indian subcontinent to fall under Islamic rule. Parts of the modern-day province were intermittently subject to raids by the Rashidun army during the early Muslim conquests, but the region did not fall under Muslim rule until the Arab invasion of Sind occurred under the Umayyad Caliphate, headed by Muhammad ibn Qasim in 712 CE. Ethnic Sindhi people constitute the largest group in the province; Sindh is also the place of residence for the overwhelming majority of Muhajirs (lit. 'migrants'), a multiethnic group of Indian Muslims who migrated to the region after the Partition of British India in 1947. The province is well known for its distinct culture, which is strongly influenced by Sufism, an important marker of Sindhi identity for both Hindus and Muslims. Several important Sindhi Sufi shrines are located throughout the province and attract millions of devotees annually.

Sindh is prominent for its history during the Bronze Age under the Indus Valley civilization, and is home to two UNESCO-designated World Heritage Sites: the Makli Necropolis and Mohenjo-daro.