Swaziland has the highest rate of HIV infection in the world.
The prince's comments came as part of a newspaper interview with the Times of Swaziland, which asked Mangaliso whether he was concerned about his own HIV status, having fathered children with several different women.
He replied that he was not scared of contracting the virus, and condemned the "scare tactics" used in the campaign against HIV.
"This [pharmaceutical] industry is making a lot of money and if there was no HIV there would be a lot of people who would lose business," he said. "What is now happening is that they are making so much exaggeration about HIV/AIDS so that they can keep their businesses afloat."
Expressing scepticism about the benefits of circumcision, the prince suggested that "water and a bath" would be equally effective in helping prevent the spread of HIV.
Groups working on prevention programmes have condemned Mangaliso's statements.
"It is very irresponsible for such a man to state such words," Tengetile Hlophe, Treatment Literacy and Advocacy Co-ordinator at Aids education charity Swaziland Positive Living, told RFI.
Statistics show that 42.2 per cent of Swaziland's population is infected with HIV, "which means that even the elders of the country are not taking HIV seriously," Hlophe says.
"This man is a role model... What are the young men in the community going to say if he's telling them it's easy, you just take a shower, you go and wash it off?"
Other traditional leaders have embraced recent anti-Aids campaigns.
Prince Masitsela, regional administrator of Swaziland's central Manzini province, volunteered to undergo circumcision and HIV testing earlier this year.
"I didn’t do all that for myself but for the nation," Masitsela, who is in his 70s, told the media.
"HIV/AIDS is a very serious issue and people should take it seriously."