I did not know this until today, but the patron saint of librarians (and archaeologists, archivists, Bible translators and school children, among other groups) is apparently Saint Jerome. Wikipedia has an article about him. He translated the Bible into Latin (the Vulgate translation). There also appears to be a story about him removing a thorn from the paw of a lion, which explains the lion that appears in some paintings of him.
Later note: a correspondent to this blog comments that St. Lawrence is the patron saint of librarians. Wikipedia certainly lists him as such, as well, along with him being the patron saint of students and chefs, among others. Thanks to my correspondent for alerting me to St. Lawrence. Another correspondent (living in the same house as me, and a theologian, to boot) points out that Jerome had some rather difficult views about women. Discussion of this is beyond the scope of this blog, but I did want to mention it in case I appear to be supporting everything he ever wrote. I am not a theologian, so I will stop there before I appear to be more knowledgeable than I actually am.
So, librarians have two patron saints! St. Lawrence was a deacon of Rome, martyred (on a gridiron, hence the chefs) during a persecution by Emperor Valerian in 258. My home town (Ipswich, Suffolk, UK) has a church dedicated to him.