Colleague spreading his stuff on my desk

Agree - I’d also tell him that anything else left on my desk will be considered abandoned and go straight into the bin.

Do you have cats? :)

Cardboard box, dump all his stuff in it, put the box well away from the desk

Are you the one in training, OP? Was he there before you and used both desks as his own?

this!

eta: or just put his stuff by the shredder/in the bin and feign ignorance...

In this context him being upset is a good thing I think, it opens the door to an honest conversation about why he is spreading his stuff over two desks and why he feels it was “wrong” if you to put it back.
so keep putting it back onto his side and use his upset to have a proper discussion.
is it personal things that really need to stay at home or does he need a bit of support around organising his work space?

Make his stuff disappear from your desk.

Exactly 💯

Dont keep moving his stuff back, dont keep accepting his manspreading. Put a stop to it, confront him.
What do you hear when I ask you
Why do you continue to do this

You're not his maid, his tidier, his room for spreading. Your not his mother or his PA,

You dont owe him anything, You dont owe him space, you dont owe him accommodation, you dont owe him time or energy, hes a colleague, a peer. Nothing more, dont people please to accomodate him.

Your time, energy and space is AS VALUABLE AS HIS.

Spill coffee on it or break it, he’s been asked once and he’s ignored that, whatever happens after that is his own fault

Have you told him why you want a clear space? I need my desk to be clean and tidy in order to feel like I can concentrate so this would really bother me. But I think some people are stubborn and if it wouldn't bother him he might just think you're being ott. You shouldn't have to explain it of course, but it might build empathy?

Is his desk big enough for him to do his job at without needing to move onto yours? Is his desk disorganised or full of papers or is it full of things actually necessary. If he is disorganised then that's the issue your manager needs to address, if he doesn't have appropriate storage then he needs to ask for drawers or book time into his diary to do a clear out/ scan and shred. This is what your manager should be addressing not just the things on your desk.

I think you need to start addressing it as soon as he does it, if he sets something down you need to say sorry you can't leave that on my desk, please find somewhere else for it.

It's another version of manspreading.

Get a box and keep piling it in then put it on the floor next to his desk.

Put some kind of barrier up at the end of your desk so he can't push it down.

Tell him to have some respect.

I always do this as I hate people invading my personal space! (And I think most people do it unintentionally)
I usually put my laptop case or a big notebook was up to the edge of the desk so that it’s much harder for people to encroach!

Three options:

He does not listen when you speak. What you are saying about your boundaries just does not register.

Or

He does hear you - and has decided what you are saying about your boundaries just does not matter.

Or

He does hear you and understand you - and has decided that he is going to control and infuriate you anyway, for fun, misogyny or sheer bloody mindedness.

Whatever his angle, he's manspreading. Bulldozing boundaries.

Email him saying 'I have repeatedly asked you to respect my personal space and not to use it for your possessions.

I see that once more you have ignored my request.

This is disrespectful behaviour and makes my work environment difficult.

In future, please use your own space for your own things.'

See what happens. Then if no behaviour improvement, bring the line manager in, to do their job.

Repetition.
He’s clearly socially unaware.

File it in B 1 N.

Toss it (not in your own bin). Deny all knowledge; why would you know what happened to his stuff? He intends to make life easier for himself at your expense. When it becomes MORE inconvenient for him to fuck you over than to behave normally and organize his work properly in the first place, he'll stop.

Similar to what @QueenArnica posted, ask him why he puts his stuff on your desk. If he huffs and moves it say, “no seriously, explain to me why you put your stuff on my desk.” Keep your tone calm, like you are bewildered rather than angry; implying he is some strange oddity rather than a rude twat. It will probably embarrass him immensely and feel very uncomfortable while he tries to come up with something vaguely reasonable to say. People hate having to say out loud that they are rude, selfish, entitled prick. Maybe that will stop him doing it again.

Add a big sign saying "Bric-a-brac 20p per item, all proceeds to the donkey sanctuary" - and then charge him at the advertised rate if he wants anything back.

Just keep doing it, he'll have to be upset or be a professional adult

Anything he leaves on your desk remove and put in a drawer. When he asks where it is say “I assumed you didn’t need/want it is as it was discarded on my desk.”

^ 😂😂😂

Put a box on the ground and shoof it all off into the box.

What are we supposed to do with him?

How about telling him next time it happens, his stuff will go into the bin rather than back on his desk. And do it. That should solve it.