Party (BSP) fell to a projected 86 seats in the 403-seat state assembly after winning 206 in the previous election.
Mayawati, 56, who only uses one name, rose from a community of "untouchables" (now known as Dalits) at the bottom of the Hindu caste structure to rule over Uttar Pradesh, a state in northern India with a population of 200 million.
She attracted strong support from Dalits and other marginalised groups who saw her as a doughty champion of the poor fighting against the ruling elite in New Delhi.
Styling herself as a "living goddess", she has often attacked the Congress party government as a corrupt and self-serving cabal that failed to tackle India's endemic poverty.
But she also drew sharp criticism for her own taste for extravagance, as well as allegations of financial malpractice within her state government -- both issues seen as major factors in the dramatic collapse in support for her.
Born into a "Chamar" family on the outskirts of New Delhi in 1956, Mayawati was studying law when she was talent-spotted by the then BSP president Kanshi Ram in the mid-1980s.
Ram persuaded her to join politics, telling her "she was born to rule" rather than to serve.
Within a decade, Mayawati had become chief minister of Uttar Pradesh for the first of her four stints in power as she battled for control in the turbulent world of politics in the northern state.
Her latest -- and by far longest -- term in office, which began in 2007, has overseen some economic development, as well as huge controversy over her building parks full of huge statues of herself and other past low-caste icons.
Public records show that more than a billion dollars was spent on the projects, but Mayawati has always brushed off allegations of arrogance, saying the parks acted as a "lighthouse" for down-trodden Dalits.
Her long-term adversary Mulayam Singh Yadav, whose Samajwadi Party was set to defeat her by a thumping margin in the elections, has often vowed to raze the parks.
Yadav, a former wrestler now aged 72 famed for his ferocious rivalry with Mayawati, is in line to become chief minister for the fourth time since 1989.
In opposition, Mayawati is likely to be a dogged opponent, but she will be shorn of the influence and power that critics say went to her head and turned her into a "first-rate egomaniac," in the words of a leaked US diplomatic cable.
The US cables released last year by the WikiLeaks website recounted a story in which she was said to have sent her private jet to pick up a pair of sandals from Mumbai.
The cables also alleged that she celebrated her birthday each year by receiving millions of dollars from "sycophantic party members, civil servants and business people", while officials vied to feed her cake.
Mayawati hotly denied all the allegations and demanded that WikiLeaks founder Julian Assange be thrown in a mental asylum.
The former school teacher, who in recent years has toned down her dress style after previously dripping in diamonds, drew enthusiastic crowds on the campaign trail.
Carrying her trademark handbag, she used her speeches to hail the improved status of Dalits and -- seeking to broaden her appeal -- also promised further help for the millions of often marginalised Muslims.
Mayawati, who is unmarried, may have hoped that large turnouts at her rallies pointed to another term in office and a step towards a bigger role on the national state.
But Tuesday's results showed that the reign of the "Dalit queen" was over for now.