Edwin Poots has been elected leader of the Democratic Unionist Party in Northern Ireland.
Mr Poots, 55, who has held several Stormont portfolios, is currently Northern Ireland's agriculture minister.
He does not intend on succeeding Mrs Foster as First Minister of Northern Ireland and will nominate another DUP candidate.
After the result was announced Mr Poots spoke about the resilence of people in Northern Ireland.
"It's that resilience that we are going to go forward and make Northern Ireland a good place." he said.
"This party has been the authentic voice of unionism and will continue to be the authentic voice of unionism under my leadership."
Sir Jeffrey represents the more pragmatic wing of the party and Mr Poots the more ideological.
The new leader-elect has courted controversy in the past over his strongly-held views on evolution and homosexuality.
As health minister, he tried to maintain a ban on gay men donating blood and opposed adoption by same-sex couples.
Many will view this as a victory for the more traditional wing of the DUP but there was another dimension to this contest.
Both candidates had pledged to reform the party and reconnect the leadership with the grassroots.
He is under pressure to take a harder line on the Northern Ireland Brexit Protocol than his predecessor did.
Some Unionists want to end co-operation with the Irish government over the Irish Sea border.
But that would be considered a breach of the ministerial code and could collapse the devolved government.
His first challenge will be to reunite the party without further dividing the power-sharing administration.