Republic of Yemen (reunified)
Who & why: North and South Yemen formally unite on 22 May 1990, ending 72 years of separate northern and southern statehood, under President Ali Abdullah Saleh. A brief 1994 civil war fails to break the union apart. Since 2014–15, however, a civil war between the Houthi movement, the internationally recognized government, and a Southern Transitional Council seeking southern autonomy has left the country's actual governance fractured among multiple authorities, even as the 1990 flag remains the country's sole legal one throughout.
What it represents: a plain pan-Arab red-white-black tricolor, deliberately stripped of either predecessor state's own emblem (North Yemen's green star, South Yemen's star-in-triangle) as a neutral symbol for the newly unified republic.