How to tell my advisor I don't want to stay in academia I don't want to stay in academia after finishing my PhD. My current research field is not exciting to me anymore, but also I am too old to change fields. Although my research and my interest were so far quite theoretically focussed, I would like to find a more applied job in R&amp;D in a big prestigeous company, helping improving future technologies. 

Now: How do I tell my supervisor? I want to avoid leaving the impression I think our research field is boring.
My supervisor tries already finding Postdoc positions for me, and probably thinks I'm quite qualified for staying in academia. So I fear to be disappointing.
How do I tell my supervisor? I want to avoid leaving the impression I think our research field is boring.


The other answers are already very good. You don't have a specifically academic problem, yours is a communication strategy issue.


be honest: in your specific case, tell your advisor as soon as possible in order to avoid a situation when too individuals want/wish each other only good and due to a misalignment it ends up in a clash;
focus on the positive side: Communicate that you are motivated to go for an industry position. It's easier than to focus on why you don't want to stay in academia.


There are always two sides of a coin. Your question sounds as if you wanted to avoid something (staying in academia) and that is always difficult to communicate, since it pushes you to defend your decision. Try to formulate it as if you were positively pulled to somewhere else. Then it's not you who is on defense, you took the active part in the conversation and usually it will be the other party to defend their position why not to do something (going to industry) is a bad move. As pointed out by others, you own a decision to do something (subjective, hence any reason is good enough), but there usually arises a need to explain why you don't want to go the default route (calls for more objective arguments, which are much harder to formulate). Your motivation for being pulled somewhere can stay vague, I wouldn't even hesitate to invoke emotions, such as I feel like I would like such a job and want to give it a try.