While Christianity came to Київська Русь – Kyivan Rus' much earlier, indeed there is a tradition at the Apostle Andrew traveled as far as Kiev, and in an encyclical letter in 867 Patriarch Photius of Constantinople wrote of Christianity having been received by the Russians enthusiastically after the Bulgarians were converted in 863, the Baptism of Kievan Rus' — a monumentous event in European Christendom — is ususally dated to 988 with the baptism of Grand Prince Saint Volodymyr - Vladimir in Corson – Корсунь in Chersonesos, today a region of Sevastopol on the Crimean Peninsula, followed by mass baptisms in Kiev on the Dnieper river. As with most people of European Christendom though, it was a women ruler who was first baptized. With Kievan Rus it was first Saint Vladimir's grandmother, Saint Olga, who became a Christian, certainly by 957 and perhaps as early as 945.

Крещение Руси – Baptism of Rus', fresco by В.М. Васнецов – Viktor Vasnetsov,
in the Патріарший кафедральний собор св. Володимира – Saint Volodymyr's Cathedral in Kyiv,
which is the Patriarchial Cathedral of the Ukrainian Orthodox Church of the Kyivan Patriarchate,
the seat of one of the three major Ukrainian Orthodox Churches, divided from each other, and bearing one another little affection:

• Українська Православна Церква Київського Патрiархату (УПЦ-КП)– the Ukrainian Orthodox Church of the Kyivan Patriarchate (UOCKP);
• Українська Православна Церква Московського Патріархату (УПЦ МП) – the Ukrainian Orthodox Church (Moscow Patriarchate) (UOC-MP); and
• Українська Автокефальна Православна Церква (УАПЦ) – the Ukrainian Autocephalous Orthodox Church (UAOC).

In some times and places such divisions are called schisms.
Of course there are Protestants, as elsewhere of countless kinds and descriptions, and Muslims and Jews in the Ukraine.
And even among those claiming allegiance to Orthodoxy, there are smaller groups including Old-Ritualists, ROCOR loyalists and the UAOC-C
(Ukrainian Autocephalous Orthodox Church Canonical – Українська автокефальна православна церква канонічна (УАПЦ-К).
Latin Rite Catholics constitute perhaps as many as one percent of the population of the Ukraine, though decendants of Poles and other Catholics
would not usually look on the person of Saint Vladimir or the date of 988 as holding the same significance as do the big-O Orthodox.
The same is not true of the Ukrainian Greek Catholic Church (UGCC) – Українська Греко-Католицька Церква (УГКЦ).
Though in Full Communion with Rome and the Pope since the Union of Brest of 1595/1596, the Greco-Catholics count Saint Volodymr as their own.