My items were stolen

Unfortunately in such cases your items can not be retrieved. The only thing you can do is to report the account involved and spread the word about the scam to keep others from getting scammed.

I was scammed out of money or conned into buying something for a scammer

File a dispute with your card company to get a refund, this can also be done with PayPal and other similar services. No need to worry about facing any repercussions as you are not responsible for unauthorized purchases and most services have measures in place in case of scams. If you don't know how to file a dispute here's simple step-by-step guides for debit cards, credit cards, and PayPal. Do this as quickly as possible as you will only have limited time.

If you were tricked into purchasing a game through Steam then the game can be refunded via Steam Support by requesting a refund and explaining what happened. You will be refunded and the game will be removed from the scammer's library. Other gaming services such as Epic Games, GOG, Uplay, and so on also have this feature. Again: Don't delay! You have limited time!

My account was hijacked

First thing to do is immediately freeze any payment info you had saved on your account (credit or debit cards, paypal, etc.) if you had any and ensure no unauthorized purchases have been made on them. If there are any then file a dispute with the company to get a refund as seen above. Next go to Steam Support's page and follow these steps. At the bottom of the page you can recover your account. Note that this process takes a few days.

If you have a mobile authenticator (which has for the most part become standard) then you don't need to worry about your items being stolen or messed with in any way. Even if you don't there'll be a trade hold for 14 days and it doesn't take that long for you to recover your account, after which you can simply cancel the trade.

Sometimes scammers will try to blackmail you by threatening to delete your account. Scammers who hijack your account won't be able to do that so don't worry. Steam requires definitive proof of ownership in the form of payment information previously used which the scammers should have no means of knowing. Even if they did get through that process it takes 30 days from the time the deletion request is approved for the account to get deleted and you can manually cancel it once you get your account back with a single click.

A lot of times accounts are hijacked through scams (most commonly the Admin impersonator scam or phishing scams) but if you don't know how your account was hijacked there's a possibility you have a keylogger virus on your computer. If this is the case then scan your computer for malware.

I accidentally put my username and password into a phishing site

Change your password immediately and scan your computer for malware.

If you want to be extra safe you can log out from all devices (except your mobile app) by going to your Steam launcher and selecting Settings > Account > Manage Steam Guard Account Security > Deauthorize all other computers now.

How could I have fallen for this scam? I feel so stupid!

You are not stupid for getting scammed. Scams can happen to anyone. Even high profile traders and YouTubers have lost their entire inventories to scammers.

Scammers will often try to shame you into staying quiet about having been scammed by making you feel stupid so the scam doesn't become known and therefore less effective; don't let them. If you have been scammed then let others know about the scam. You don't need to tell people you were scammed; just that someone attempted to scam you. Be sure to give details on the scam and how to spot it.

Did something else happen or do you need help?

Create a post about it and we will gladly help you as best as we can. Don't hesitate to ask "stupid questions"; we don't judge.

If you'd be more comfortable asking using a throwaway account you are welcome to do so.