What's the most boring subject you've ever studied?

Banking regulation. didn't really matter what the book said, what mattered was what the representative of the regulator understood them to say. if that turned out to be "there can be no transaction logs" in direct contravention of the book, then so be it.

Postal regulations were far more fun, at least there was a rational reason for most of those. The Postmaster is still the Person with the Vote regardless of the books; but they're usually interested in getting the mail moved instead of asserting their power and will cooperate.

In 12th grade I took a course on anatomy. You had to memorize things like the names of all the bones and muscles, which I found very boring and tedious. It put me off medicine. Of course, it's important that medical professionals know such things, so anatomy is certainly not "useless".

In University? French. The official language of the country is French and I've been learning French since I was in school. I've failed it though by missing the exams due to work (couldn't make it in time).

History.

Looking back, the primary goal of each textbook and teacher was to do their best to make sure nobody would ever voluntarily pick up a history book for the rest of their life.

Decades later I wound up reading a biography of a moderately interesting person, which led me off to history in a sideways manner. Now I'm a minor history buff.

Funny, history wasn't the only subject the public school system seemed to be trying to induce Pavlovian avoidance reflexes to...

I'm not sure anything I've studied is "useless", but the most boring (for me) was geography.

Most of the subjects I studied in school bored me to tears. But when I studied them on my own, I found them fascinating.

Honestly, I can't think of a single subject that I've found useless or boring. Even things that sound dull as dirt on the surface get very interesting when you dig below the surface.

Probably public/administrative law. I actually enjoyed a lot of the more notoriously boring subjects like company law but administrative law was intolerably dry.

I never studied it in an academic setting, but to this day when I have to read a data protection clause my eyes glaze over after a couple of lines.

Public and Civic laws. This contained stuff like what are the rules governing the judiciary, executive and the president.

Highly tedious stuff.

Abstract algebra.

Not lying, just too abstract for my liking.

Comparative literature was really boring, I hated that elective in college.