When we were in Lisbon a few years ago, one of my must-dos was to visit Livraria Bertrand.
It was almost a religious experience for me to walk through the door of a bookstore that was established in 1732.
Although it was destroyed in the great Lisbon earthquake of 1755, it was moved to the very location it still occupies in 1773. It has been open and continually operating in that same location for 235 years -- three years longer than the United States has existed as a country!
Bertrand has expanded to become a big chain store company with 56 locations throughout Portugal. however, the one we visited on Rue Garrett, just a few blocks from our apartment is the original.
There is a bookstore in Paris - the Galignani that claims to be the oldest, but Bertrand predates it by 30 years.
While looking for the specific dates and statistics, I ran across this web site:
Pretty informative for anyone travelling throughout Europe and in the need of a bookstore.