Answer: Researching this question is a bit tricky. First, you have to include or exclude the martyr popes, Saint Peter who was crucified by the Romans would probably be at the top of the consideration list. Then one has to consider the various historically dubious situations of life that various popes got themselves into, mostly in the early years of the papacy. Wikipedia has a nice article breaking down a list of popes that died violently, listing seven murders, all between the years 882 and 984. That seems a little quirky, that popes in order to be considered murdered have to have lived between 882 and 984. That would also be a big disappointment for those folks who advocate conspiracy theories about the death of Pope John Paul I in 1978. Perhaps we should check a few other sources.

Asking CHATGPT, the absolute bastion of internet misinformation (sometimes) but a good source things to be fact-checked, a list of ten papal murders was obtained. Again the death dates ranged from Pope John VIII in 882 but extended to Pope Damasus II in 1048. Consulting another internet source, the Academic Dictionaries and Encyclopedias, listed seven definitely and nine "alleged" papal murders from Pope John VIII in 882 to Benedict XI in 1305. Their list also added Pope John Paul I in 1978 citing conspiracy theories and a book written by David A. Yalop.

So after this brief bit of research, the conclusion is that it is probably impossible to determine exactly how many popes have actually been murdered but give lots of remembrance to the martyr popes. Those guys were really murdered and it is hard to leave them off the list.



References
• List of Popes Who Died Violently Wikipedia
• List of murdered popesAcademic Dictionaries and Encyclopedias (this article mostly based on Wikipedia information)
• Klein, Christopher 10 Grisly Papal Deaths, https://www.history.com/news/10-grisly-papal-deaths