It's no secret that China is less than welcoming of missionaries and overt religious practices that may be seen to disrupt the social order. However, there are a huge number of churches and mosques throughout China, and it's a widespread myth in the West that you get in trouble for reading the Bible here. In fact, at many universities, the Bible is required reading for Western Civ and Lit classes.

Proselytising is illegal and has been throughout the PRC's history. If you come here to spread a religion and you're caught, you'll be sent packing. Certain groups (Scientologists, Falun Gong) are banned as well, though both of these are much more recent. There are English churches which are typically limited to foreigners, and then there are Mandarin churches which the regular citizen may attend. Money given to the church or mosque or temple is not without State management, and so on.

There are only five religions (groups, really) that are permitted in China: Buddhism, Taoism, Islam, Protestantism, and Catholicism. These are all monitored by the government through the State Administration for Religious Affairs. However, worth noting is that the Chinese Catholic Church is not formally tied to the Vatican and, under communism, never has been. When the PRC took power, all Catholic and Protestant missionaries were kicked out of the country as the State turned against Christianity and its Western roots. 1957 saw the creation of the Chinese Catholic Church, formally the Chinese Patriotic Catholic Association.

The State Administration for Religious Affairs is also behind the policies regarding the appointment of various Lamas under Western Buddhism, such as the controversy involving the Panchen Lama as Gyancain Norbu as chosen by the State versus Gedhun Choekyi Nyima as chosen by the Dalai Lama. This occurred at the end of the 1980s, and before then there was not such a dispute over the Panchen Lama's reincarnation. However it closely mirrors an issue between Beijing and the Vatican regarding Catholicism, and a big reason the two are still separate. If the Chinese Catholics formally link to the Vatican, then the appointing of clergy would become a major point of tension. The current policies are arranged such that the authority of the Party is not in question in regards to religious practice.

In the past 70 years, Many temples and churches were destroyed, particularly during the Cultural Revolution. Same goes for mosques and other religious buildings, though a few have survived such as the Great Mosque in Xi'an. While there are quite a few churches in China today, they are largely the result of recent construction and not left over from earlier buildings.

Also, not specifically mentioned by your question, however it's also worth nothing that Albania under Hoxha was official Atheist. I'm not sure if it was the only country to ever have that as the state religion, but I believe that's the case.

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I'm having a horrible time getting this comment posted properly. I think it's something with my network. Forgive me if there are multiple copies or other issues.

I'll include one of the other examples, Yugoslavia. There was an anti-religious drive after the Second World War, when socialist Yugoslavia was formed. In this particular case, I think it is best to view it as two different processes: secularization and struggle between systems of belief. Two are obviously related, but not the same.

Secularization, although radical and in the first years coupled with state repression (that again had another, political dimension itself), was fundamentally the same as in any modern secular state. It concerned things like: no religious courses in school (they became facilitative first, and were excluded in 1952), civil marriage (religious ceremony was possible, in fact common, but without legal status), civil books of births and deaths, and so on. Along with all that, Churches were hit quite hard by other measures there were not specifically anti-religious. Maximum landholdings obviously greatly affected large church properties, even though for individual parishes maximum was set two or three times as high as it was for most people. Press limitation also meant the end of most Church press, for example for Catholic church only one paper remained.

Struggle between systems of belief involved mostly the religious behavior of Communist party members. For example, it was considered incompatible to attend religious ceremonies and keep the party membership. In the first post-war years it was quite radical, so members were sanctioned for example for attending a funeral because it was conducted by a priest. Such measures were repealed by the early 50s, as it was recognized that they ferment unnecessary discord between CP members and general public, but still overly or overtly religious behavior was discouraged and often sanctioned within Party.

There is an almost universally accepted narrative of anti-religious repression in Yugoslavia. And there certainly was some. Hundreds of priest were tried, imprisoned or killed, not necessarily in that order. Much of the Church property was seized, and their press was mostly banned. However, all of that was not specially directed against Church - many political opponents, especially former collaborators with fashist, nazi or quisling regimes, were killed or imprisoned, most of oppositional press was stopped, large landholdings, industrial and commercial property was seized. But when clergy at the time, late 40s and 50s, complained about prosecutions of religion they mostly referred to the measures included above under secularization.