HP said its 25.50 pounds-per-share cash offer -- representing a 79 percent premium that many HP shareholders found excessive -- had been accepted by investors representing 87.34 percent of the company's shares, well ahead of the 75 percent threshold needed.
Buying the Cambridge, England-based firm, whose software searches unstructured data like emails, phone calls and tweets that do not fit into traditional databases, was one of a raft of surprise radical reforms announced by HP's Apotheker in August.
Apotheker also decided to close HP's Palm Web OS tablet and smartphone unit and sell or spin off its PC division.
The rushed announcements and concerns about the lofty price offered for Autonomy sent HP's stock, and Apotheker's credibility, plunging.
But according to analysts, it would have been nearly impossible under British takeover rules for HP to extract itself from the Autonomy deal.
Former eBay Inc
Controversy about the deal was further stoked by an extraordinary spat between Autonomy's founder Mike Lynch and HP's rival Oracle
Oracle's outspoken CEO Larry Ellison said he had also been approached but had no interest in buying Autonomy at what he called an absurdly high price.
Autonomy will operate as a separate business unit with Lynch leading the division, the company said.
HP's offer to purchase the remaining Autonomy shares also remains open, it said.
(Reporting by Poornima Gupta in San Francisco and Paul Sandle in London, editing by Bernard Orr)