19 December 1989
Two rival political organisations in Zimbabwe, the Ndebele-dominated Zimbabwe African People's Union (ZAPU), led by Joshua Nkomo, and the Shona-dominated Zimbabwe African National Union (ZANU), led initially by the Reverend Ndabaningi Sithole and later by Robert Mugabe, finally merged following consensus reached in 1987 to form a new political party called the Zimbabwean African National Union-Patriotic Front (ZANU-PF).
References

SAHO, Mugabe announces the merging of ZANU and ZAPU, [Online],Available at:www.sahistory.org.za,[Accessed:27 November 2013]|

cws,Timeline: Zimbabwe, [Online],Available at:www.cws.org,[Accessed:27 November 2013]