Not to be mistaken for the country of Malta, they are the smallest country in the world. Wikipedia has them listed as the sovereign Military order of the Knights of Malta.
There are actually a couple "Knights" groups that descend or claim to descend from the various knights hospitallers...and often nowadays they run charities or ambulance services.
But the KOM are a lay religious order that runs charities all over the world.
Today the order has 12,500 members, 80,000 permanent volunteers, 13,000 medical personnel including doctors, nurses, auxiliaries and paramedics. The goal is to assist the elderly, the handicapped, refugees, children, the homeless, those with terminal illness and leprosy in five continents of the world, without distinction of race or religion. In several countries including Ireland, Germany and France, the local associations of the Order are important providers of first aid training, first aid services and emergency medical services. Through its worldwide relief corps, Malteser International, the Order is also engaged to aid victims of natural disasters, epidemics and armed conflicts.
One item of trivia: they issue their own passports.
It retains its claims of sovereignty under international law and has been granted permanent observer status at the United Nations. SMOM is considered to be the main successor to the medieval Knights Hospitaller.
This makes it easier for them to work in war zones.
I first ran into them while working in Liberia. They were sponsoring leprosy clinics there, and I knew the nun who supervised these clinics, going from village to village to check people and give them medicines.
Nowadays, leprosy is easy to treat, with pills. The real problem is if the person is not diagnosed early enough, they end up with nerve damage and deformities, which then have to be treated with surgery.
But when I was working in Liberia, we started having a lot of civil unrest, and I made plans to leave the country, only to find that my employer refused to give me an exit visa.
So it was the KOM ambassador helped me to get out of my contract so I could leave: luckily for me, since there was a coup the next week (followed by an economic collapse, and ten years of civil war) and if I had been stuck there, I would have been in physical danger.
So another Catholic group that does a lot of good but gets little or no publicity.