"I will give my all to this organisation for the next six months... but in the summer I'll step down as your Director-General," he told staff in a group email.
"If I followed my heart I would genuinely never want to leave. However, I believe that an important part of leadership is putting the interests of the organisation first," he added.
Hall took up his post in 2013, tasked with restoring the reputation of the world's biggest broadcaster after late presenter Jimmy Savile was exposed as one of Britain's most prolific child-sex offenders.
But the corporation now faces the fallout of last week's shock equal-pay ruling, which could end up costing it many millions of pounds (dollars, euros), and hostility from the government over the licence fee.
An employment tribunal ruled the corporation discriminated against female presenter Samira Ahmed, paying her one sixth of the amount given to Jeremy Vine for hosting a similar show.
The ruling opens the door to many other claims.
The BBC is also facing pressure from Britain's new government, headed by Prime Minister Boris Johnson, which accuses it of bias in reporting in the recent general election.
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