Almost 450 rhinos were killed in South Africa in 2011, prompting warnings that unless poaching is checked the species' survival could be in jeopardy.
In the face of rising demand in Asia for rhino horn, which is now worth more than gold, diamonds, heroin and cocaine, official figures showed 448 rhinos were lost to poaching last year.
The figure, which includes 19 critically endangered black rhinos, is well above the 333 South African rhinos killed in 2010, and almost three times the number poached in 2009, wildlife organisations WWF and Traffic said.
The increase in poaching is thought to be driven by demand for rhino horn in Asia, particularly Vietnam, where it is a luxury item, a purported cancer cure and even used as a hangover remedy.
Poaching is continuing at high rates in the first few days of 2012, with eight rhinos killed in South Africa's world-famous Kruger National Park. Last year the park lost 252 rhinos - more than half the total killed in the country.
Andrew McVey, species programme manager at WWF-UK, said: "More rhinos were poached in 2011 than has been recorded in any single year before. If left unchecked, poaching gangs could put the survival of these iconic species in jeopardy."
Last year also saw WWF declare the Javan rhino extinct in Vietnam after the last remaining animal was found killed with its horn removed.
Tom Milliken, Traffic's rhino expert, said: "Rhino horn has gained popularity among wealthy Vietnamese elites and business people to give as a gift, when currying political favour or taking as an antidote to overindulgence. But killing endangered rhinos to mitigate a hangover is a criminal way to see in the New Year."
The rise in poaching comes despite increased law enforcement efforts, which have seen more arrests by the South African authorities and an increase in sentences imposed by the courts.
Dr Morne du Plessis, chief executive of WWF-South Africa, said: "Rhino poaching is being conducted by sophisticated international criminal syndicates that smuggle horns to Asia. It's not enough to bust the little guy - investigators need to shut down the kingpins organising these criminal operations."