Parliament speaker Jacob Mubenda gave permission for a joint session of the House of Assembly and the Senate to debate a motion that would trigger impeachment proceedings against Mugabe.
"This motion is unprecedented in the history of post-independence Zimbabwe," Mubenda declared.
Lawmakers from across the political spectrum have called on Mugabe to quit after the military seized power and tens of thousands of citizens took to the streets to demand the 93-year-old's resignation.
They accuse him of allowing his ambitious wife Grace to plunder the country and to usurp his power.
That prompted the current crisis as the army, alarmed by Grace's rise, deployed armoured vehicles on the streets and took power.
There were tense protests outside parliament as hundreds of demonstrators -- from rival political parties -- shouted for Mugabe to go.
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