These are all churches that currently hold Orthodox services. If I can't find evidence of a church that holds regular services (house churches count), then the country does not have an Orthodox Church listed. I have included Oriental Orthodox Churches. If you know of a country with an Orthodox Church that I have missed or overlooked, please let me know.
Bahamas
Annunciation Greek Orthodox Church, Nassau
Bahrain
St Mary's Indian Orthodox Cathedral, Manama
Bangladesh
Due to the Portuguese influence in Bangladesh, the majority of Christians there are Roman Catholic.
I can find no evidence thus far of any Orthodox Christians.
Please pray for an Orthodox Church in Bangladesh!
Barbados
St Paul Ethiopian Orthodox Church
Belarus
Church of St Sophia of Slutsk, Minsk
Belgium
Orthodox Church of the Holy Apostle and Evangelist Matthew, Leuven
Belize
Benin
The majority of Christians in Benin are Roman Catholic.
I can find no evidence thus far of any Orthodox Christians.
Please pray for an Orthodox Church in Benin!
Bhutan
There are approx. 15,000 Christians in Bhutan. I am unable to find evidence of any Christian Church operating in Bhutan, as Christians are only allowed to worship in their own homes.
Please pray for the Bhutanese Christians!
Bolivia
Santa Maria y San Marcos Church
Bosnia and Herzegovina
Cathedral of the Nativity of the Theotokos, Sarajevo
Botswana
They're also looking for pictures of the church.
Brazil
Church of St Zinaida the Martyr, Rio de Janeiro
Brunei
The majority of Christians in Brunei are Roman Catholic.
I can find no evidence thus far of any Orthodox Christians.
Living as a Christian in Brunei is extremely difficult.
Please pray for the Bruneian Christians!
Bulgaria
St Alexander Nevsky Cathedral, Sofia
Burkina Faso
Please pray for an Orthodox Church in Burkina Faso!
Burma
The majority of Christians in Burma are Protestant.
I can find no evidence of Orthodox Christians in Burma.
Living as a Christian in Burma is extremely difficult.
Please pray for the Burmese Christians!
Burundi
I can find no evidence of an Orthodox Church in Burundi.
Please pray for a Burundian Orthodox Church!