How do I remove WiFi networks from the WiFi drop down list OS X?

If you created the guest network, then you can get rid of it by changing the settings on your router to eliminate it. As has already been explained, the list you're looking at is a list of networks that are visible. You can't make networks on that list go away any more than you can make your neighbors house go away because you want a better view of the mountains. Not unless you own the network in question, in which case you can manage it on your router.

The same is the case for me. The old service and router is disconnected and the service has been discontinued. But this connection is still in the drop down menu on my Mac. Makes NO sense to me. It is not listed in the networks, advanced area.

Your Mac will not "jump" to that network unless you previously joined it.

Assuming you did, go to System Preferences>Network.

Click the Advanced button. On the WiFi tab, locate the network and click the "-" sign to remove it from your preferred networks. The only way to remove it from the list of available networks is to stay out of range of it.

I have the same problem. In the past I created a guest network that I want to remove now. I did remove it from the list in /preferences/network/advanced/...but it stays in the dropdown list (Gasten ZWW27 and Gastnetwerk van Ernest Briet see picture). Is there a way to get rid of it ?

Many thanks

EB

Physically move out of range of those networks.

Aha, that simple and logical.

Many thanks

Ernest