Of course, you can go to both Portugal and Spain in three weeks. It depends on your priorities. Once you are in Seville, it's just as easy to go to Lisbon as Barcelona. So the idea that entering another country is some sort of travel no-no is a bit absurd.

And I am really surprised you are proposing Marbella. A town that appears on 'must-see' lists... absolutely never.

One thing you might consider is that there is no such thing as a 'must-see.' It is simply a question of what inspires you. But that should come from your own armchair travel first. Clearly you are drawn to Andalusia (you are not alone). so start there. You can fly right to Seville.

If I were in your shoes.... I'd be tempted to fly to Portugal first (yes, this will take longer), spend two weeks going from Porto to Lisbon (Or the other way around), fly to Seville, spend a week in Andalusia, and go onto Scandinavia from there.

That way, every day of your three weeks you will experience a 'must-see.' Though I personally don't subscribe to the idea.

If you need inspiration about Portugal, here is an excellent trip report (with photos). It's not mine. https://www.fodors.com/community/eur...gress-1697432/

Unfortunately, our trip to Spain did not eventuate in 2025. However, we are now planning to do this in 2026. We are looking at the first 3 weeks in Spain followed by 2 weeks in France, returning home from Paris. We have been to Provence, Paris and Dordogne previously.
At this stage, we would appreciate any comments about the Spain itinerary. We do have some flexibility with this schedule
Fly into Madrid, 2 nights,
train to Toledo, 1 night
train to Cordoba, 2 nights
train to Ronda, 2/3 nights, hire a car to visit nearby villages
train to Seville via Cordoba, 3 nights
train to Granada, 3 nights
fly to Barcelona, 4 nights
train to San Sebastián, 3 nights

I must admit that I would find this itinerary too rushed for my tastes. Only 2 nights in Madrid? (Jet lagged nights?) Only 4 nights in Barcelona? No time for Girona or Montserrat or any of the other gems near Barcelona? If it were me (it's not!) I'd skip San Sebastian until you have time to include Bilbao and other parts of northern Spain and I'd add that time to Barcelona and / or Madrid. Or, for that matter, add a night to Toledo -- more than enough there to keep one busy. Your trip, your call! Whatever you choose, you'll see some amazing places.

Perhaps you should take a closer look at the train schedules.
For example : to travel from Toledo to Cordoba , one has to go through Madrid,
Barcelona to SS takes many hours by train , etc..

Thanks Kja, I do not want a rushed itinerary. I will relook at this.
Danon, thanks for the reminder about checking train schedules. I thought there is a direct train from Toledo to Cordoba.

Yes two nights in Madrid is not enough time. There is too much to see and do there, same with Barcelona. Both places are great bases for day trips such as El Escorial or Segovia from Madrid or Montserrat from Barcelona. As May is increasingly becoming prime travel season so people can avoid the summer heat bear in mind that there will be many other travelers and places are crowded and take time and reservations most likely in advance. Perhaps you don't need three nights in Granada. It is lovely and interesting although we had to spend three nights but it was in late fall and there were road closures because of heavy rainstorms, so we needed the extra day to wait it out.

Your itinerary is not bad except for the beginning. Tack on another day to Madrid, or I give you permission to skip Madrid entirely Then you can distribute those days elsewhere as you see fit.

As others have pointed out, one could spend their entire vacation exploring each of your destinations. Their suggestions are just the tip of the iceberg. However, there is nothing wrong with what you are proposing.