Is there an upper limit for the level in DND?

3R and 3E stipulate that the core is level 20 (equivalent to the level of the world's top experts 10, which is actually a joke), because there is a "legendary field" above level 20, and levels 2 1~40 are called legendary levels. Reaching this level means that you are already a legend (actually a joke).

Up to level 40.

4E The highest level is 30, and each level 10 is a field. The intensity is basically proportional to the 40th grade of 3R.

Finally, family rules are the most important.