Swansea East MP Carolyn Harris has won the Welsh Labour deputy leadership election.
The result - run under an electoral college - comes despite Ms Harris winning fewer votes from members than her rival, Cardiff North AM and former MP Julie Morgan.
The result was announced at the Welsh Labour conference in Llandudno.
The election - the first for a deputy leader in Welsh Labour - was held under an electoral college, where the votes of party members are weighed alongside trade unions, affiliated organisations, and elected parliamentarians.
Ms Harris told delegates that the result had "knocked me sideways".
"But while I always hoped I could win, I've never quite believed I would. Which makes this moment all the more special," she said.
"I would of course like to pay tribute to Julie Morgan, who brought to this campaign the same energy, passion and commitment that has characterised her lifetime's service to Welsh Labour. I look forward to campaigning with her for Welsh Labour in the months and years ahead.
"I will never forget the trust that members of our Welsh Labour family - members, Trade Unionists and affiliates - have placed in me.
"And I will also work day in, day out to earn the trust and support of those who cast their vote for Julie.
"I am proud beyond words to be deputy leader of such a party. And I promise you one thing - I won't let you down."
Welsh Labour leader and First Minister Carwyn Jones said: "For the first time ever we have a deputy leader of Welsh Labour.
"I want to congratulate Carolyn Harris on her win and I look forward to working with her very much.
"I also give my heartfelt thanks to Julie for her campaign, and the superb contribution she has already made to Welsh Labour and will continue to make in the years ahead."