The Durban high court ruled in favor of the uMkhonto we Sizwe (MK) party in the latest of a string of court battles between Zuma and his former political party, the ruling African National Congress (ANC).
The ANC tried to stop the 82-year-old's new party from using the MK name, alleging intellectual property theft.
The name of the opposition MK is identical to that of the armed wing of the ANC, which Nelson Mandela led from exile during the apartheid era.
"The application is dismissed with costs," a court authority said in a televised ruling.
Zuma, who was forced out of office in 2018 under a cloud of corruption allegations, is campaigning for MK in a bid to relaunch his political career and weaken his former party, the ANC.
"I'm over the moon that the ANC has been shown that they can't fight the MK, we are unstoppable," MK's leader Jabulani Khumalo told national broadcaster SABC.
South Africa goes to the polls on May 29 in what is expected to be the most competitive vote since the advent of democracy in 1994.
According to recent polls, the ANC is on course to score below 50 percent for the first time.
Earlier this month, Zuma won a battle against a decision by the electoral authorities to bar him over a contempt conviction, allowing the scandal-tainted politician to stand in the poll.
The charismatic Zuma, who was president from 2009 to 2018, still carries considerable political clout and has recently garnered major media attention.
A recent poll by South African think tank Social Research Foundation predicted the MK would be the second largest opposition party, with 13 percent, with the ANC on 36 percent and the official opposition Democratic Alliance securing 25 percent.
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