Redditor Ngugi compiled this interesting and extensive information about the fantasy warrior women in Tolkien’s Middle-earth:

Éowyn is the best known but far from only valiant human woman in JRR Tolkien’s Middle-earth. This an account on those who armed for battle, whether at need or as profession.

In the First Age there were three human houses/folks known as the Edain (forefathers of the Dúnedain). The Edain allied with the Elves in Beleriand. The first of the Edain was the House of Bëor.

Bëor’s folk had able women, led by Emeldir, wife of Lord Barahir. Their land suffered ill in the wars in Beleriand against Morgoth, the original Dark Lord (art by jubah);

“At last so desperate was the case of Barahir that Emeldir the Manhearted his wife (whose mind was rather to fight beside her son and her husband than to flee) gathered together all the women and children that were left, and gave arms to those that would bear them; and she led them into the mountains that lay behind, and so by perilous paths, until they came at last with loss and misery to Brethil.”

~ Silmarillion; III; XVIII (art by Jonas Åkerlund)

The second Edain folk was the House of Haleth, named after a chieftainess who led them through a battle and to new homes. They had their own language, culture and customs (Unfinished Tales; IV; I):

“One of the strange practices spoken of was that many of their warriors were women, though few of these went abroad to fight in the great battles. This custom was evidently ancient; 1 for their chieftainess Haleth was a renowned Amazon with a picked bodyguard of women.”

“1 Not due to their special situation in Beleriand, and maybe rather a cause of their small numbers than its result. They increased in numbers far more slowly than the other Atani, hardly more than was sufficient to replace the wastage of war; yet many of their women (who were fewer than the men) remained unwed. [Author’s note.]”

~ Unfinished Tales; IV; I; Notes (image by TurnerMohan; I mention that most of Haleth’s folk would had brown or dark hair)

In the Third Age we learn that the Easterlings living in the North, Wainriders who conquered land near Mirkwood, had a similar custom; women were an established part of the home defence (image by RealmsofGold).

In the late 19th century many of the Wainriders’ dwellings, storehouses and fortified camps of wagons were destroyed by Northmen;

“But most of them had perished in the attempt; for they were ill-armed, and the enemy had not left their homes undefended: their youths and old men were aided by the younger women, who in that people were also gained in arms and fought fiercely in defence of their homes and their children.”

~ Unfinished Tales; III; II (image by Tancredi Valeri)

“I am a shieldmaiden and my hand is ungentle” spoke Éowyn (RotK; II; V) and the Rohirrim apparently had this ancient custom (art by Magali Villeneuve).

In a draft to the LotR, Tolkien considered it was more frequent some centuries prior (HoME 8; III; II):

“Eowyn says that women must ride now, as they did in a like evil time in the days of Brego […] when the wild men of the East came from the Inland Sea into the Eastemnet.”

This only concern humans, an account on Elf women is found here.

A good essay on the development and themes of the character of Éowyn is found here.

In case you enjoyed this and would like to read further Tolkien lore posts about characters, themes, objects and events, here is an index.

Source: Ngugi