The Kingdom of Kotte (Sinhala: කෝට්ටේ රාජධානිය, romanized: Kottay Rajadhaniya, Tamil: கோட்டை அரசு), named after its capital city, Kotte, thrived as a Sinhalese kingdom in Sri Lanka during the 15th century.

Under the leadership of Ming-backed Parakramabahu VI, Kotte achieved significant territorial expansions by conquering the Jaffna kingdom and the Vanni principalities, unifying the country under a single banner. This period also witnessed a punitive invasion against the Vijayanagar dynasty, resulting in the capture of a port that was subsequently transformed into a vital trade route.

The Kotte Kingdom faced challenges during the Sinhalese-Portuguese War, encountering opposition from rival Sinhalese kingdoms, namely the Kingdom of Sitawaka and the Kingdom of Kandy. Eventually, Dom João Dharmapala handed over Kotte to the Portuguese, leading to the establishment of Portuguese Ceylon. The remnants of the kingdom were absorbed into Sitwaka and Kandy.

Etymologically, the term "Kotte" is believed to originate from the Sinhalese word "kotta" and the Tamil word "kōttei," both meaning fortress. The fortress was founded by Nissankamalla Alagakkonara, and the Alagakkonara family, associated with the city of Vanchi (identified with Kanchipuram in Tamil Nadu), played a significant role in Kotte's history.

Kotte was initially established as a fortress by Minister Alakesvara during the reign of Vikramabahu III of Gampola to safeguard against South Indian invasions on the western coast. Later, Parakramabahu VI made Kotte the capital in 1412, enhancing its citadel and constructing a new royal palace. The kingdom strategically waited for the severance of ties between the Vijayanagara Empire and the Jaffna Kingdom before capturing the Vanni region, consolidating power under Prince Sapumal.

Parakramabahu VI's reign saw the zenith of the Kotte Kingdom in 1450, following the conquest of the Jaffna kingdom. However, by 1477, regional kingdoms gained prominence, and a new kingdom was founded in the central hill-country by Senasammata Vikramabahu, leading to a rebellion against Kotte in 1469.

The capital was shifted to Kelaniya in 1509 under Parakramabahu IX and remained there until 1528.

The arrival of the Portuguese in 1505 marked a turning point in Kotte's history. Despite a complex plan to mislead the Portuguese about the kingdom's location, a trade agreement was established. The downfall of Kotte began with the "Wijayaba Kollaya" in 1521 when King Vijayabahu VII's sons mutinied, dividing the kingdom among themselves. The divided kingdoms of Kotte, Sitawaka, and Raigama emerged.

In 1565, Dharmapala of Kotte abandoned the capital due to attacks from Sitawaka and sought Portuguese protection in Colombo. The Kotte Kingdom officially ended in 1597 when Dharmapala gifted it to the Portuguese throne.

The military of the Kotte Kingdom played a crucial role in its rise and fall, with firearms being introduced and adopted, and notable commanders, including Alagakkonara, Parakramabahu VI, and Manikka Taleivar.

Trade flourished due to Kotte's proximity to the important port of Colombo, with Moorish merchants dominating until the arrival of the Portuguese. The kingdom engaged in spice trade, gemstone exports, and controlled pearl trading post the conquest of Jaffna.

The Kotte era witnessed a golden age of literature and art, with royal patronage fostering notable poets like Thotagamuwe Sri Rahula Thera and the creation of literary works such as "Lowada Sangarawa" and "Buduguna Alankaraya." Buddhist education institutions and Ayurvedic medical books also flourished during this period.

Religiously, Buddhism was the state religion, and Parakramabahu VI built a shrine for the Sacred Tooth Relic. Hinduism also held prominence, with Buddhist temples housing shrines for Hindu deities. The Portuguese conversion to Roman Catholicism impacted the religious landscape, making the last king, Don Juan Dharmapala, a Catholic.

Battaramulla, a village providing rice to the king's palace, and Baththotamulla, known for royal flower gardens in an area called Rajamalwatta, were significant locations during the Kotte era.