The phrase "alien peoples" is correct and usable in written English.
It can be used in contexts discussing different cultures, societies, or groups that are considered foreign or distinct from one's own.
Example: "The anthropologist studied the customs and traditions of alien peoples to gain a deeper understanding of their way of life."
Alternatives: "foreign cultures" or "distant societies".
As the Alexandrian kingdoms spread throughout the East, the Greeks were forced to extend their interest to alien peoples and the records of the past.
Although the dissimilarities between the artistic expressions of different cultures and different times are great, there are also similarities; for the borrowing of art forms from distant and occasionally alien peoples was a common practice.
This restatement was especially important since the deportation policies of Assyria (for the northern kingdom in 721 bc) and Babylonia (for the southern kingdom in 597 and 586 bc) had introduced alien peoples and religious practices into the Israelite scene.
But it would go against the pattern of world history if alien peoples patronized English for very much longer than necessary.
The history of Afrikaans literature is the history of the Afrikaners, an alien people whose literature is a testimony to that state of alienation.
"There are conventions held in town, and the alien people like to come here and congregate," she said.
It was a sport that most blacks considered — if they considered it at all — "the brutish, alien pastime of a brutish, alien people".
Although McKinley had not entered the war for territorial aggrandizement, he sided with the "imperialists" in supporting ratification, convinced that the United States had an obligation to assume responsibility for "the welfare of an alien people".
The ancestors referred to here, he's clearly referring to Gentiles who have come into the church as Gentiles and then now occupy their role as part of this alien people too.
No Longer at Ease by Chinua Achebe "We returned to our places, these Kingdoms, / But no longer at ease here, in the old dispensation, / With an alien people clutching their gods".
As a consequence, by the 4th century, Christians tended to regard Jews as an alien people who, because of their repudiation of Christ and his church, were condemned to perpetual migration (a belief best illustrated in the legend of the Wandering Jew).
