Well, kind of.
You have to own them in the first place.
Here's what I did.
I took a photograph (from 90 degrees directly overhead) of the area of a map on my camera. I used my camera because I wanted a good quality, hi-resolution, image.
And then I uploaded the image to my phone.
Being a smart phone it means I can zoom right in to the image at a good quality resolution.
So now, when out and about, you have a high-quality, OS version, of a map of the area you want!
OK, so it's no good if you want to use the map with a compass, but if you are just out, following a footpath, and want a map of your area...well, there you are. It works perfectly for a day's walk. Like I say, it has limits, but if you just want a route map of somewhere (which is probably most of the time) then having them stored on your phone is convenient and handy. Yeah, I know you can get some maps for some smartphones, but these are good, reliable, OS maps with all useful features on them rather than those featureless driving-style maps and, of course, can be used offline so you don't have to worry about a bad signal.