Black July: Eighteen Tamil political prisoners at the Welikada high security prison in Colombo are massacred by Sinhalese prisoners, the second such massacre in two days.

The Welikada Prison Massacre took place during the 1983 Black July pogrom against Sri Lankan Tamil minority in Colombo, Sri Lanka. Fifty-three prisoners were killed inside a high-security prison. No one has been convicted of crimes relating to these incidents.

Black July (Tamil: கறுப்பு யூலை, romanized: Kaṟuppu Yūlai; Sinhala: කළු ජූලිය Kalu Juliya) was an anti-Tamil pogrom that occurred in Sri Lanka during July 1983. The pogrom was premeditated, and was finally triggered by a deadly ambush on 23 July 1983, which caused the death of 13 Sri Lanka Army soldiers, by the Tamil militant group Liberation Tigers of Tamil Eelam (LTTE). Although initially orchestrated by members of the ruling UNP, the pogrom soon escalated into mass violence with significant public participation.On the night of 24 July 1983, anti-Tamil rioting started in the capital city of Colombo and then spread to other parts of the country. Over seven days, mainly Sinhalese mobs attacked, burned, looted, and killed Tamil civilians. Estimates of the death toll range between 400 and 3,000, and 150,000 people became homeless. Around 8,000 homes and 5,000 shops were destroyed. The economic cost of the riots was estimated to be $300 million. The NGO International Commission of Jurists described the pogrom as a genocide in a report published in December 1983.Sri Lankan Tamils fled to other countries in the ensuing years, and a large number of Tamil youth joined militant groups. Black July is generally seen as the start of the Sri Lankan Civil War between the Tamil militants and the government of Sri Lanka. July became a period of remembrance for the Sri Lankan Tamil diaspora community around the world.