Is High Sierra the most recent OS I can install on my MacBook Pro, late 2011? I have enough storage (140 GB) and memory (8 GB) for Catalina.

Yes.

High sierra (10.13) is the newest for a 2011 Macbook pro.

The next version is 10.14:

How to upgrade to macOS Mojave - Apple Support

And it requires:

MacBook Pro introduced in 2012 or later

Have a nice day!

Macs made before 2012 lack a video hardware technology called "Metal" that OS 10.14 and higher require. It cannot be retrofitted because MacBook Pros have their video/graphics hardware integral with and soldered to the logic board, and it cannot be removed and replaced.

"Metal" is a combination of an Application-Program Interface (API) software connected to substantial hardware-assists built into the graphics cards that Apple requires for rendering graphics in Mojave and later.

Apple deems the Graphics Hardware in the Mac Pro 2011 too old and not capable enough to run Metal in a reasonable way, because almost all would have to be "simulated" in software, and would be far too sloppy and too slow.

I have been experimenting with a hobbyist hack that allows the installation of Mojave on a Mac Pro 2010, which is otherwise not qualified to run Metal unless and until a substantially more modern Metal-capable graphics card is installed.

Its performance with the old card is wonky and slow, similar to what you see in Safe Mode on your MacBook Pro 2011 (Safe Mode does not load Graphics acceleration).

That setup (Mojave without metal-capable graphics card) borders on being unusable. Screen re-draw is slow, and certain areas of the screen remain blacked-out. Web Videos will often not play, and some Apps like Maps show a window border, but the contents remain blacked-out, no matter how long you leave it.

There is good reason why Apple does not support Mojave and later on your computer. Your computer's graphics processor(s) are not up to the job.