Halep was initially banned for four years for two separate anti-doping rule violations. But the Lausanne-based Court of Arbitration for Sport (CAS) ruled her suspension should be reduced to nine months, a period she has already served.
"The CAS Panel has unanimously determined that the four-year period of ineligibility... is to be reduced to a period of ineligibility of nine (9) months starting on 7 October 2022, which period expired on 6 July 2023," CAS said on Tuesday.
Now that the 32-year-old Romanian is eligible to compete, she could be granted a wild card to this year's French Open or Wimbledon.
"Throughout this long and difficult process, I have maintained my belief that the truth would eventually come out, and that a just decision would be reached, because I am and always have been a clean athlete," Halep said in a statement.
"I cannot wait to return to the tour."
Halep was suspended in October 2022 after she tested positive for roxadustat - a banned drug that stimulates the production of red blood cells - at the US Open that year.
She was also charged with another doping offence last year due to irregularities in her athlete biological passport (ABP), a method designed to monitor different blood parameters over time to reveal potential doping.
Halep, who vigorously denied the charges, has said that she would most likely be compelled to retire if the initial four-year ban was maintained.
She blamed contaminated supplements for her positive test at the US Open and accused the International Tennis Integrity Agency (ITIA) of charging her with an ABP violation after the group of experts who assessed her profile learned her identity.
In response to the ruling, ITIA chief executive officer Karen Moorhouse said: "An essential element of the anti-doping process is a player’s ability to appeal, and the ITIA respects both their right to do so, and the outcome."
An independent tribunal accepted Halep's argument that she had taken contaminated supplements but said the volume she ingested could not have resulted in the concentration of roxadustat found in her positive sample.
However, the CAS Panel said that while Halep should have been more careful when using the supplement, she did not bear significant fault for the violation.
Also, the ABP charge was dismissed on the basis that it was appropriate to consider that the sample given in late 2022 was shortly before a surgery and that Halep had said she was not going to compete for the rest of that year.
The Professional Tennis Players Association said the CAS decision "underscores the need for sensible reform to an unjust system that fails to protect (the players' rights)."
