What are the benefits of spreading religion to other civilizations?

[Puppier]

I know there are benefits to spreading religion to city states, but what about other civ's?

 

[Cedbird]

One of them is if you can spread your religion to the majority of the other Civ and they did not discover the religion / have the holy city then they welcome your religion and you get a + Diplo hit

 

[Browd]

There is a modest positive diplo modifier for spreading a religion to a civ that does not have its own religion. Conversely, there is a negative diplo modifier if you persist in sending GPrs and missionaries into a civ that has its own religion after it has warned you off.

But the real benefit of spreading your religion to other civs comes from your founder belief. Eight of the nine founder beliefs provide tangible advantages when your religion spreads to foreign civ cities (some require your religion be a majority religion in a city, while others only require that you have one or more followers in the city or, in the case of Interfaith Dialogue, that you use a Missionary or Great Prophet to spread):

• Ceremonial Burial: +1 Happiness for each City following your Religion
• Church Property: +2 Gold for each City following your Religion
• Initiation Rites: +100 Gold when each City first converts to your Religion
• Interfaith Dialogue: Gain Science when a Missionary or Great Prophet spreads your Religion to cities of other religions
• Peace Lovingi: +1 Happiness for every 5 followers of your Religion in non-enemy foreign cities
• Pilgrimage: +1 Faith for each foreign city following your Religion
• Tithe: +1 Gold for every 4 followers of your Religion
• World Church: +1 Culture for every 5 followers of your Religion in other civilizations

The remaining founder belief (Papal Primacy) applies only to religion spread to CSs.

 

[Smokeybear]

A lot of benefits, from all those. But my favorite is Tithe, in particular for small/tall civs that don't naturally produce a lot of gold from limited lands and resources. By the end of some games, I can have anywhere from 50-100+ gpt coming in all the time just from that. If you are playing domination, you can get 150+ gpt easy from Tithe. Only downside is a lot of micromanaging missionaries and prophets to get there. It does get very tiresome after a while.