Christianity came to North Africa in the Roman era. According to historian Theodor Mommsen what is now Mediterranean Algeria was fully Christian by the fifth century. A notable Berber Christian of Algeria was Saint Augustine (and his mother Saint Monica), important saints of Roman Catholicism. Christianity's influence declined during the chaotic period of the Vandal invasions but was strengthened in the succeeding Byzantine period. After the Arab invasions of the 7th century, Christianity began to gradually disappear.
Currently, North Africa is primarily Muslim: Islam is the state religion of Algeria, Libya, Morocco and Tunisia. While the practice and expression of other faiths is guaranteed by law, the same legal framework tends to restrict minority religions from actively seeking conversion to their religion, or even building or repairing churches. Converts to Christianity may be investigated and searched by the authorities as well as punished. There is some evidence that there has been an increase in conversions to Christianity among North African Muslims in recent years, even though in many cases the government will not change the religion from Islam on any citizens' identity cards. Despite this, the total number of Christians remains very low relative to the populations of these countries. In 2009, the percentage of Christians in Algeria was less than 2%. In this same survey, the UNO counted 100,000 Roman Catholics and 45,000 Protestants in the country.Although Christians are a religious minority in Algeria, churches built during the French and to a lesser extent Italian rule can still be found.