Lusaka - Hakainde Hichilema, who was released from custody after treason charges against him were dropped, is a self-made entrepreneur who has made five unsuccessful attempts to become the Zambian president.
He alleges that the 2016 election was rigged and, as leader of the opposition United Party for National Development (UPND), he has refused to recognise President Edgar Lungu.
Hichilema, 55, accused the authorities of election fraud, and of undermining his campaign by banning rallies and allowing violent attacks on his activists.
An articulate speaker, he drew large crowds to his rallies, ran a slick social media campaign and worked hard to shed his image as an elitist lacking the common touch.
But he again failed to win office by a slim margin.
He spent the last four months in custody after a bizarre incident in which he allegedly put Lungu's life in danger when his convoy failed to make way for the presidential motorcade.
The high-speed road drama was caught on video camera, and Hichilema was charged with treason.
The charges were finally dropped on Wednesday - the day his trial was due to begin.
Hichilema was born to a poor family in the southern district of Monze, and says his "grit and determination" at school won him a priceless scholarship to the University of Zambia where he graduated in 1986 in economics and business administration.
He then took an MBA degree at the University of Birmingham in Britain.
He started off small, buying and selling houses, eventually becoming one of the country's richest businessmen with major interests in finance, ranching, property, healthcare and tourism.
At the age of 32, he was Zambia CEO of Coopers and Lybrand consultancy accountants, and he has sat on the boards of several large Zambian corporations.
Despite his series of election defeats, Hichilema still hopes to win power.
He has promised to build a business-friendly Zambia and attract investment, while at the same time pledging to alleviate hardship among the country's millions of poor.
On his website he describes himself as a "Christian and a philanthropist" who funds clinics, schools, boreholes and dam building.
Before his release, he marked his 100th day in jail saying in a statement "we habour no hate for anyone as we believe that everything that happens in life is for a purpose".
He described the conditions inside prison as "atrocious" and "inhuman".
Hichilema is married and has a daughter and two sons.
When he was arrested, Amnesty International said Hichilema and the five other accused were "victims of longstanding persecution."