Using the British Library's "Comics Unmasked" exhibition as a springboard, the Department of History and Classics delves deep into history for a selection of medieval manuscripts that could certainly be considered as early comic strips.
The library's Medieval and Early Manuscripts Blog gives a shoutout to the 11th-century Bayeux Tapestry, characterized by Bryan Talbot and others as “the first known British comic strip," but the curators don't stop there. For instance, there's the Holkham Bible Picture Book (1327-1335), with its beautifully colored sequences from both the Old and New Testament, which is "sometimes described as England’s first graphic novel." Julian Harrison, the library's curator of early modern manuscripts, points out that it even employs banners for dialogue, much like word balloons in modern comics.
There's also the Silos Apocalypse with its depiction of "Daniel the Superhero," and the Queen Mary Psalter (1310-1320), which uses 223 images and captions to tell the story of Moses. Harrison promises more about medieval "comics," but for now you can read about them here and here.