Mick Cash has been elected as the new head of the Rail, Maritime and Transport union (RMT), succeeding Bob Crow.
The 54-year-old beat four rivals in a ballot to become the new general secretary.
Mr Cash, who has been a member of the RMT and its predecessor National Union of Railwaymen for 35 years, stood in as acting general secretary after Mr Crow died in March.
Mick Cash, the RMT's senior assistant general secretary, said Mr Crow's death had rocked the trade union movement, both in this country and around the world.
The thousands of messages of condolence from every part of the globe are a testament to the courage, leadership and strength that Bob shared with so many people.
Whilst Bob Crow's funeral itself will be a strictly private affair, his friends and family recognise that many people will want to show their solidarity, respect and support, both on the day itself and on May Day.
These arrangements give everyone a chance to play their part.
Trade unionists from across the country will attend the funeral of rail union leader Bob Crow today.
The Rail, Maritime and Transport union said Mr Crow's family have asked for the funeral service at the City of London Cemetery and Crematorium to be private.
But trade unionists, friends and colleagues of Mr Crow, will be invited to line the route of the funeral procession.
The procession will include trade union banners and flags and will end at the cemetery gates.
The funeral of RMT leader Bob Crow will take place on Monday, March 24, with the service being private, the union announced today.
The trade union movement is in shock after the sudden death of rail union leader Bob Crow, who passed away early this morning aged 52Read the full story ›
Tim O'Toole, chief executive of FirstGroup and former London Underground managing director, said he was "shocked and saddened" by the news of Bob Crow's death.
Mr O'Toole said:
I worked with Bob both during my time at London Underground and here at FirstGroup.
He was a tireless and powerful advocate for his members and was dedicated to the railways and public transport.
Our deepest condolences go out to Bob's family, friends and colleagues.
Bob Crow's brother said he believed the union leader suffered a heart attack in the early hours of today and paid tribute to the "loveable little rogue".
Mr Crow's older brother, Richard Crow, told Sky News: "It's very sad. It was about 7am that I got the call (from my sister). I presume some time in the night he had some problems. We're really trying to find out exactly what happened.
"We grew up together in Chigwell in Essex and he was a very likeable chap - no matter what people said about his politics.
"He was honest, he looked after the people he was supposed to look after, and he was a great man as far as honesty and beliefs went. He was a person who believed in justice."
When asked what Bob was like when he was younger, Richard replied: "He was one of those loveable little rogues, one of those guys that had bundles of friends. He would be a cheeky chappie Cockney kid. He was a lovely kid to grow up with."
Mayor of London Boris Johnson said he was shocked and saddened to hear about the death of union leader Bob Crow.
Paying tribute to the improvements in London Underground made by his political opponent, he said his death leaves a massive gap behind and praised his indefatigable defence of his members views and interests.