No doubt about it. Based on this Truth Social post, Donald Trump is mentally ill.

 

As reported with a straight face at The Hill, 8/18/2023

and

Salon, 8/18/2023

and

Washington Examiner, 8/18/2023

and on and on

Merriam-Webster defines megalomania as  

a delusional mental illness that is marked by feelings of personal omnipotence and grandeur