The Islamic Defenders Front (FPI) vowed to mobilise 30,000 demonstrators to protest the US artist's June 3 performance in Jakarta and to intercept her at the airport.
"We will stop her from setting foot on our land. She had better not dare spread her satanic faith in this country," FPI Jakarta chairman Salim Alatas told AFP.
"Her style is vulgar, her sexual and indecent clothes will destroy our children's sense of morality. She's very dangerous," he said.
The US pop diva, famed for her outrageous outfits and provocative performances, has sparked opposition in other Asian countries with her "Born This Way Ball" global tour, which kicked off in Seoul last month amid protests.
But the FPI, notorious for making threats and often failing to follow through, will face opposition from 40,000 fans planning to attend the sold-out show in Indonesia.
Little Monsters -- as Lady Gaga fans are called -- tweeted their determination to see the pop idol perform in Indonesia, 90 percent of whose 240,000 million inhabitants identify themselves as Muslim.
"Little Monsters Indonesia vs FPI. I'm ready to fight," Bentaniokevin tweeted to the LadyGagaIndo Twitter account.
"What?!! The FPI want to cancel Lady Gaga's concert? They don't know art!! She is the lady of art!! GAGA I'm waitin for you.. See u soon," nataliahaman tweeted.
One page on Facebook, which is wildly popular in Indonesia, was seeking dancers for a Lady Gaga flashmob, which sees people perform a choreographed dance in a public place.
The flashmob is "to show our appreciation to Lady Gaga for planning to visit and to tell others who don't approve of her that there's nothing wrong with being her fans," said Anggiat Sihombing, an 18-year-old university student who set up the LadyGagaIndo account.
"We like her because she is a famous musician who makes use of her popularity to do good deeds, like establishing a foundation to protect kids who have been bullied."
The Lady Gaga Indonesia Facebook page has more than 42,000 "likes".
"Lady Gaga is not an ordinary human being. She uses her popularity to defend minority groups, especially gays and lesbians," said Hartoyo, general secretary of gay rights group OurVoice, who goes by one name.
"I would die for her," he said.
Despite the opposition to her tour, the "Poker Face" singer has not toned down her performances -- at the Seoul show on April 27 she rode onto the stage on horseback, wearing a black bodysuit and an enormous black metal headpiece.
There were small protests outside the show, with two foreign Christian protestors holding placards that read "Lady Gaga. Go home!" and "Sexual purity, virginity, fidelity", while about 20 South Korean Christian activists prayed.
In the Philippines, a youth organisation urged people to stay away from the star's May 21 concert, saying it posed a threat to moral values in Asia's largest Catholic nation.