We leave on a cruise out of Portsmouth, so we are looking for a hotel convenient to the port and any sights that are must see.
I don't have a hotel recommendation, my visits to Portsmouth were day trips from Chichester, but I highly recommend the Mary Rose - https://maryrose.org/
I liked Premier Inn, Portsmouth Dockyard on Queens Street, overlooking the historic dockyard and a very short walk to The Hard. I sprang for a room with a water view and looked out at Spinnaker Tower and the Warrior, a Victorian-era warship. The Ship Anson pub is just around the corner and is all I hope for in a pub. From The Hard you can access buses and trains. As VAP said, visit the Mary Rose, but, if time permits, also visit the Victory and the Warrior.
The Mary Rose is at the Portsmouth Historic Dockyard along with the HMS Victory, Warrior, and other ships. If really interested in historic ships, it would be easy to spend an entire day there. Admission is a little pricey, but tickets are good for a year. Even if only visiting once, the dockyard is worth visiting.
We have reservations at nearby Lysses House Hotel for an upcoming trip. It may be too far from the port for what you want.
We have stayed at the Holiday Inn Express right at Gunwharf Quays, an excellent location for the historic dockyards and restaurants, easy to get to by train or bus as the station is nearby.
The cruise port though is a bit away, not far, but a 30 to 40 minute walk, sort of a toss up whether you want to be close to the sights or the port.
another person with a good experience at the Holiday Inn Express at Gunwharf Quays.
Right at the mall, lots and lots of restaurants (mostly chain, but some good chains), next to The Spinnaker.
One small issue - if you have a number of electricals you might stick in an extension cord or multiplug. It may have changed in the couple of years since I stayed there but the wall opposite the bed has zero outlets. I managed fine but forewarned is forarmed.
Very very convenient. Next to the station, close to Dockyard...On the shore.
We stayed at the Premier Inn Portsmouth Dockyard in 2023. It is the ideal location for visiting the Dockyard. I preferred the Victory to the Mary Rose, but there are some steep stairs/ladders to negotiate on the Victory,
https://www.premierinn.com/gb/en/hotels/england/hampshire/portsmouth/portsmouth-dockyard.html
I just stayed at the Royal Maritime Hotel earlier this month for a couple of nights before taking a ferry to Normandy. I found it to be a fine place that was very conveniently located.It is very close to the Historic Dockyards (you could spend a day there easily), and an easy walk to the waterfront. As I recall, the breakfast was included. In addition to the Dockyards, the Spinnaker Tower and the D-day museum were highlights for me, as were a couple of good local pubs. An added bonus for my trip was the availability of a laundry room.
You won't want to stay somewhere close to the cruise port as it's situated in a rough part of town and there's nothing particularly worthwhile in the vicinity. I suggest you look at staying close to the dockyard as others have mentioned and take a taxi to the cruise terminal.