Sharapova was appointed Goodwill Ambassador for the UN Development Program in 2007 with a special focus on Chernobyl recovery efforts.
The three-times Grand Slam winner was born in Siberia a year after her parents were forced to leave a Belarusian region affected by radiation from the explosion at the Chernobyl nuclear power plant in neighboring Ukraine.
Shortly after taking on her Chernobyl role, she donated $100,000 to youth projects in Belarus, Russia and Ukraine, former Soviet republics where the after-effects of the disaster are still felt.
In a statement ahead of Saturday's 22nd anniversary of the disaster, UN Secretary General Ban Ki-moon said, "On this occasion, the United Nations honors the emergency workers who labored heroically at the damaged reactor; the hundreds of thousands who were evacuated from surrounding areas with little hope of return; and the millions living in contaminated areas who have long feared for their health."
The Chernobyl disaster was caused by overheating following a disastrous experiment involving fuel rods, which was ironically aimed at improving safety.
While the initial Soviet cover-up was condemned by the West, it is almost certain that the authoritarian regime in place at the time, which sent hundreds of workers to their certain death in the operation to seal the damaged reactor, averted much greater loss of life using means that would have been inaccessible to an open, democratic society.
Findings issued in 2005 by the UN Chernobyl Forum - a consortium of UN agencies led by the World Health Organization, the International Atomic Energy Agency, and UNDP - and subsequent studies confirmed that the majority of people in the affected regions have little to fear from radiation, but need better social and economic opportunities.
Vast areas, including beyond the Soviet Union, were contaminated by the fallout of the explosion. More than 300,000 people were relocated. Some 5 million people live in areas of Belarus, Russia and Ukraine classified as "contaminated" by radioactive elements.
There is no accurate data on the number of deaths, due to Soviet secrecy over the disaster. The Chernobyl Forum said 56 people, mainly rescue workers, were killed at the scene, and another 4,000 died of thyroid cancer shortly afterwards.
Several million more people are believed to have been exposed to varying degrees of radiation.
The disaster is thought to have released at least 100 times more radiation than the atom bombs dropped on the Japanese cities of Nagasaki and Hiroshima in WWII.
Ukraine has plans for a new shelter over damaged reactor four, and signed a contract with a French contractor. The current badly-worn protective shelter is being repaired and reinforced by Russia, in a project funded by the international Chernobyl Shelter Fund comprising 28 countries and run by the European Bank for Reconstruction and Development.