Train from Madrid Airport to Seville

To take a fast train that gets you to Seville’s Santa Justa train station, you need to travel 8 miles into the city to Madrid’s Atocha train station. That can take anywhere from 20 minutes in optimal conditions by taxi up to 1 hour by bus from the airport. And yes— buying your train ticket in advance can cut the price down to €10- sometimes even less. Spain now has four fast train companies with the entry of IRYO just two days ago. IRYO uses the “Red Arrow” trains of Italy’s Trenitalia train company.
These trains can travel up to 223 miles per hour. The other fast train companies are Renfe, Spain’s national train company which uses AVE trains and AVLO, Renfe’s low-cost train option. The fourth choice is low-cost Ouigo, which is run by SNCF, France’s national train company.
You can now buy online tickets which load the ticket on to your mobile phone for departures up to and including August 30, 2023 at www.TheTrainline.com
The Trainline is a reputable ticket agency based in the UK. Many travelers prefer to use TheTrainline website because it’s simple, quick, gets you your online ticket now for next to nothing and avoids waiting for Renfe to begin selling tickets 60-90 days in advance of your travel day, and spares you the frustration of spending hours trying to buy tickets on the ever-malfunctioning Renfe website.
It obviously depends on your travel date, but looking at the current train schedule, it appears there is one fast train departing close to the top of the hour and through the afternoon. I would buy the €20 or €30 ticket for the train that gives you three hours to get through the formalities at the airport and transfer to Madrid’s Atocha train station. With any extra time, you can have a late lunch before boarding your train .
If you wait to buy the ticket when you arrive, the train could be sold out or you could be
looking at a €100 ( or more) ticket. Some tickets for November 29 are already €120. As with airline tickets, train tickets become increasingly expensive the longer you wait to buy them.

If you buy in advance the best practice is to buy a fully refundable or flexible ticket in case your flight does not arrive on time. Those are usually the most expensive. You can also buy your ticket on your phone while you are in the air on the plane if you have internet access once you know for sure that your flight is going to arrive on time. Otherwise just wait until you get there. There is a train the Cercanias from the airport to Madrid Atocha, the train station you need to go to in order to catch your train to Seville . There will be plenty of English speaking airport personnel to help you and point you on the right direction. Spain is one of the top tourists destinations in the world.
All major airports have information on their websites on how to get where you need to go. You just have to Google that. Here is info on all your options
for Madrid https://www.aeropuertomadrid-barajas.com/transportation/madrid-airport-bytrain.htm

Another option would be to look at the cost of changing your ticket to fly to Sevilla. Most major airlines have done away with most change fees, and even a difference in fare could be worth it over the cost and hassle of getting into the city for the train.

For the route between Madrid and Sevilla Renfe is currently the only operator. Iryo is scheduled to introduce competing service there at the end of March. Alvo, Renfe’s discount operator only “plans to launch in 2023”

The choices are Iberia and Vueling for a handful of flights. It will be interesting to see if the competition between the four companies running fast trains throughout Spain has the effect it had in Italy where
Alitalia, the national airline, went bankrupt as passengers abandoned the airline for domestic trains.

Thanks very much for all the informative answers! The best info is always from other travelers :)

the effect it had in Italy where Alitalia, the national airline, went bankrupt as passengers abandoned the airline for domestic trains

While some Alitalia may have lost some travelers to trains, that's not at all why they went bankrupt. Almost never a profitable endeavor, it was largely seen as a PR effort/political vanity project. They were burdened with high cost structures and inefficiencies, which were a political challenge to shed as the market liberalized. Even after privatization, they burned through billions in state-funded bailout monies over a relatively short time.

But there were two nails in the coffin in mid-2020: The economic crisis of the pandemic finally made it politically unsavory to pump more money into the black hole—especially when healthcare was breaking at the seams. And the EU was investigating previous state aid to the company as possibly illegal and anti-competitive, a problem further aid would have magnified.

Replying to Scudder:
Alitalia also suffered from poor service. We have traveled to Europe three times in the last five years. Using American, Iberia, Air France and Alitalia. By far the best was Air France and the absolute worst was Alitalia. When flight attendants treat passengers like they are on the Soup Nazi line it's not a good thing. Crew disappeared for several hours during the flight and passengers had to help themselves in the galley. Pillows and blankets dropped on the floor in the aisles were not picked up but, rather, stepped over by the crew until final approach. And the food was horrible. So much for Alitalia.

Check to see if you can fly direct to Seville. I just checked Delta SFO-SVQ...MAD-SFO in January(SVQ=Seville) $841. Looks better to me than going from Madrid airport to Atocha to Seville.
buen viaje Brad