On 12 June 1993, Chief M.K.O. Abiola of the Social Democratic Party (SDP) stood against Bashir Tofa of the National Republican Convention (NRC) in a presidential election that observers across the divide — domestic, African and Western — regarded as the freest and fairest in Nigerian history. Abiola, a Yoruba Muslim from the South-West, ran on a 'Muslim–Muslim' ticket with Babagana Kingibe and won across regional, religious and ethnic lines, including in Tofa's own Kano State. The unofficial count credited Abiola with about 8.3 million votes (≈58%) to Tofa's 5.9 million.
On 16 June, a Federal High Court in Abuja (Bassey Ikpeme J.) issued an ex parte injunction at the suit of the Association for Better Nigeria (ABN, fronted by Arthur Nzeribe) restraining the National Electoral Commission (NEC) from releasing results — even though the Transition to Civil Rule Decree had explicitly ousted court jurisdiction over the election. NEC Chairman Professor Humphrey Nwosu, defying the order, partially released state-by-state results showing Abiola clearly ahead. On 23 June, the Babangida-led Armed Forces Ruling Council issued Decree 13 annulling the election in its entirety, without ever releasing the final official count.
Mass protests erupted in Lagos, Ibadan and the South-West, with deaths in police shootings during early July. On 26 August Babangida 'stepped aside', installing an unelected Interim National Government under Chief Ernest Shonekan; on 17 November General Sani Abacha removed Shonekan in a palace coup. Abiola declared himself president at the Epetedo Declaration on 11 June 1994 and was arrested for treason on 23 June 1994 — he would die in detention on 7 July 1998, the day before his planned release. His wife Kudirat Abiola was assassinated on 4 June 1996 leading the campaign to restore his mandate. In 2018 President Buhari posthumously declared Abiola a GCFR and moved Democracy Day from 29 May to 12 June.
In February 2025 — thirty-two years after the annulment — General Ibrahim Badamasi Babangida published his memoir 'A Journey in Service' (Bookcraft, Ibadan) and conceded for the first time on the public record that Abiola won the 12 June 1993 election, that the annulment was a mistake, and that it occurred outside his personal direction. The admission was launched in Abuja on 20 February 2025 before a gathering that included Presidents Tinubu, Buhari, Obasanjo, Goodluck Jonathan and former Heads of State Gowon and Abdulsalami; Aliko Dangote and others raised over ₦17 billion at the event for Babangida's planned presidential library. The book's June 12 chapter is now part of the documentary record of the annulment alongside the Justice Niki Tobi-led Justice Reform Committee files and the Oputa Panel testimonies of the 2000s.