In addition to the National Healthcare System:
https://www.expat.com/forum/viewtopic.php?id=902977
you also have the option of the Private Healthcare System (PHS).
Each Insurance Company provides its Health Insurance solutions by targeting market segments and insurance coverages: Individual, Family, Dental, Senior,... and establishes agreements with the existing PHS networks in Portugal. A wide range of facilities such as 24/7 medical assistance, online appointments with doctors, access to specialists and exams, annual health checkups, access to second medical opinion, price reduction (for consultations, exams, treatments, operations and hospitalisation), ... are considered in most of the available health insurances.
For each one, you can carry out a cost simulation based on your age & medical requirements.
Sales channels, Trading partners / "Agentes comerciais"
Banking system is a widely common channel for the insurances distribution, and Health Insurances in particular. You also have the option of commercial insurance agents spread throughout the country.
Agreements / "Acordos", "Convenções"
Each PHS Network in Portugal provides agreements and partnerships with private hospitals, medical clinics and doctors all over the country.
Each PHS network covers all medical specialties and most of municipalities/"concelhos" in mainland Portugal, but also in the Azores and Madeira islands. This means you'll have access to high-quality healthcare services in most cities. Even if you've settled in a tiny village in the portuguese countryside, a larger network can mean a shorter drive to your doctor's office or private hospital/clinic.
In Portugal, the main Private Healthcare System - PHS networks are:
(Sorted by portuguese market share, 2020)
1st Multicare (Fidelidade)
2nd Médis (Ageas Group)
3rd Advance Care (Tranquilidade/Generali Group)
4th Future Healthcare
5th Allianz Care