For broadest selection:
Digikey and Mouser. For both it is important to go via their German digikey.de and mouser.de pages so that you get prices displayed in EUR. At checkout, they will add VAT (19%) and stuff gets delivered without any customs hassle (incoterms DDP). Free shipping above 50EUR (the 50EUR is net/without VAT). Digikey free shipping is with UPS (2 days), Mouser with FedEx (also 2days). Do not use the US websites (digikey.com/mouser.com) - you would get free shipping above 60$, but VAT/customs processing is then not included...
Lots of stuff (I mostly buy standard semiconductors, electrolytics, connectors there): Reichelt (reichelt.de). Beware, their displayed stock status is not always right, they don't have a direct link between their web shop and warehouse systems, they seem to do a batch update every day or two. Bigger orders ship slower (frequently 4 or 5 days).
Someone mentioned Conrad: Better check out Voelkner (voelkner.de ) - they are owned by the same company, same warehouse, same items, most of the time considerably cheaper. Not really for electronic components, but they are often good for other workshop supplies, electro-mechanical stuff, various industrial supplies, oh, and they have good prices for MeanWell power supplies.
Pollin (pollin.de) has a weird mix of surplus and China-import stuff, components, tools, etc. My source for hook-up wire and some other random stuff.
TME (tme.eu) is a reliable distributor. I just don't buy there that often because they never have everything I need for a project, and the other companies I have to order from end up having everything I could have ordered from TME. They have items that are hard to get in small quantities elsewhere, though.
Farnell (farnell.de) is similar to Mouser/Digikey, but usually a bit more expensive. They won't ship to private individuals, though, only businesses or universities.
Bürklin (buerklin.de) has been mentioned above. I rarely order there, but they have some items you can't get elsewhere in small quantities.
Aliexpress and Banggood will now handle the VAT/duty stuff for orders below 150EUR according to new EU regulations (i.e. the seller will pre-pay and add a code showing that VAT/duty has been paid to the shipment), so no hassle there. Above 150EUR, import processing is more difficult, it depends on the shipping method how it works. Shipping time varies with selected shipping method, the slowest option has taken about 4 weeks for my latest orders).
LCSC.com in China has good prices and has had stuff in stock that was unobtainable anywhere else during the semiconductor crisis, but shipping is expensive and customs/duty processing cumbersome if you don't have a DHL or FedEx account that can be billed directly.