Maria Sharapova appears to be an Eastern Orthodox Christian.
She's not involved in partisan politics, but is involved in post-nuclear disaster work.
Maria Sharapova was born in Nyagan, Russia. She grew up mostly in Sochi, Russia and Bradenton, Florida.
Sharapova shows every sign of being deeply religious. She said in one interview that the one piece of jewelry she never takes off is the cross that her parents gave her when she was a young girl.
She also credits God with giving her the talent she was able to develop through dedication and hard work. She said,
What tennis has brought me has been incredible. God gave me a talent, but it was up to me to play my part in it. I don't believe in just God-given talent, you have to work for everything you earn and I think the combination has helped me.
What is only slightly less certain is to which denomination of Christianity Sharapova belongs. I'm almost certain that she's Eastern Orthodox, and not entirely because every other website that asserts a denomination agrees. Her parents are from Belarus, and the vast majority of Christians from that country are Orthodox, so I'd say that's a pretty good bet.
Child of Chernobyl
Sharapova doesn't get involved in the political scene in either the country of her residence, the U.S., or the country of her birth, Russia. Russian President Vladimir Putin is apparently a fan of hers, however. In 2012 he publicly congratulated her talent and skill after she won the French Open that year. And Sharapova expressed her pride at being Russian. She didn't necessarily express pride at having Putin as her president, but she didn't seem to be involved in the anti-Putin protests either.
The issue closest to Sharapova's heart is nuclear disaster. Her parents lived in Gomel, Belarus during the Chernobyl nuclear disaster in 1986, but left while her mother was pregnant with her in order to escape the fallout. And in 2007, the tennis champion joined up with the United Nations to help alleviate on-going effects suffered by those who still live in that area–one of whom is her grandmother.
In light of the Japanese nuclear disaster in 2011 and the 25th anniversary of Chernobyl, Sharapova wants everyone to know that the effects from such an incident lasts for decades:
[E]ven though something like that happened such a long time ago, it still causes many people on a daily basis [health risks]. Especially kids that were born [then], and now are having kids. You also find that they have something in their body that's not allowing them to live a normal life from the pollution.
So even though she's not involved in the partisan, it looks like this is an issue for which she'll be advocating for a long time to come.