Has anybody been rejected by the uni even though the prof agreed to supervise?

If I'm not mistaken, it's standard that professors don't have absolute power to accept any prospective student they agree to supervise - at least in the social sciences and humanities. There is usually an independent panel(s) that goes through all the applications and determine who should be accepted. However, professors do have a lot of say and usually if you've got the OK from them you'd be fine.

I'm curious if the program you're applying to is directly tied to funding? If yes then your supervisor might have even less power to influence the outcome. I was accepted to one of the unis I applied to but got rejected for funding because the admissions committee didn't rank my application high enough despite my prospective supervisor's efforts.

Hi there, I was just wondering if anybody has gotten rejected by the uni even though the prof has previously agreed to supervise? I'm planning to apply for a PhD this year, and I was just curious about how often this could happen. If anybody has experienced this, could you share why the uni rejected your application? Thank you!

The only reason I could see this happening (aside from funding-related issues), is that the supervisor would be taking on too many PhD students than their work conditions (or contract) allow for, and so they have to draw the line somewhere.

This would be quite rare. I've never heard of it happening. The circumstances I could envisage it occurring would be:

1) The candidate is clearly unsuitable e.g. does not have an appropriate first degree or does not meet language requirements
2) The candidate lied about qualifications
3) The offer is tied to funding. Often these are separate processes and the professor will often not have much say over who gets funding, but if they are linked then failing to get funding, which is common, could lead to rejection.
4) Professor's workload, as Phoenix mentions.

The only reason I could see this happening (aside from funding-related issues), is that the supervisor would be taking on too many PhD students than their work conditions (or contract) allow for, and so they have to draw the line somewhere.

A professor from another department that where I am applying told me he was interested to take me and would talk with admission chair. However, unfortunately I was rejected form the university. In this case how should I inform the professor and is there any way to change the admission decision?