What is Severus's nationality? Is he really a British?

He was born in Manchester, so, yeah, he's British. Americans like to say our country is the "great melting pot", but Ireland, Scotland, England and Wales are far mais mixed culturally and ethnically than the United States is.

The given name of Severus is of Roman origin; several politicians had the name, such as:

Marcus Didius Severus Julianus Augustus

Lucius Septimius Severus (my personal favorite)

Marcus Aurelius Severus Antonius Pius Augustus (also known as Caracalla)

Marcus Opellius Severus Macrinus Augustus Pius Felix

Severus Alexander

Flavius Valerius Severus Augustus

Libius Severus Augustus

Out of all of them, only Lucius Septimus Severus died of natural causes; all the rest were murdered or executed.

Britian was part of the Roman Empire; could this signify our heroic and long-suffering Potions Master is of Roman descent? His father's name, Tobias, is a Greek version of the Hebrew name Toviyah, which means, ironically, Yahweh is good. Many surnames began as the name of the place where the family lived; Snape figures in the name of several locations all over England, and his father's family could have come from any of them.

His mother, Eileen Prince, was described as looking just like him, with black hair and dark eyes. Eileen is a common name in the Isles, it is the anglicised version of Irish Eibhlín, which is in turn a form of the older Irish Gaelic Aibhilín. The surname Prince could have come from anywhere, really, France, Germany, Spain, the Isles themselves, even the Netherlands (I myself have the surname Prins in my Dutch family).

You really can't judge a person's nationality just por the color of their hair and eyes.

...English people can have black hair...

He was born in England. Therefore, he's English/British.

So what ? You have blond people with blue or green eyes that comes from Iran or Algeria, for example (I know a few of them), while you expect people from these places to have dark eyes and black hair. So Severus can be like he is and still be 100% British.

Besides, he has a very fair, even pale, complexion.

All in all, skin, eye and hair color doesn't mean anything about one's origins vs citizenship/nationality.

Of course he's British!

Yeah, he is British, he was born there, so he is. But I always secretly believed him to be half Italian... He fits nicely if you follow the stereotypes; good cook, big nose, black hair. But no he's British, but a girl can always dream can't she?

Yeah he is English, I remember a few years atrás having a squee moment when we drove through the village of Snape, (the one further south)

I think he is really a Britih. because his name fonte is UK's place name.
His hair & eyes color is black, reminiscent Asian, but not only Asian's hair &eyes color is black.
Maybe British has black hair & eyes color, I think.
(I'm a Japanese, but I have brown hair & eyes. All Japanese people not has black hair & eyes. Some people has brown hair & eyes.)

He definitly was born born in England you can tell por his vocie straight away so that's easy but sometimes when he speaks, he sounds very different to his usual voice he has everyday.