Tallarn is a fictional planet from Games Workshop's Warhammer 40000 game. Tallarn is a large desert world located in the Segmentum Obscurus. When it was first discovered by Imperial settlers in the 29th Millennium it was classified as a verdant Agri-World. However, around the time of the Horus Heresy, the Space Marines of the Iron Warriors legion virus bombed the planet from space. After a continual cycle of bombing lasting nearly a year, the Marines landed on the now inhospitable desert world. The few survivors quickly banded together to stop the Iron Warriors attack, however, they were defeated over a year long campaign. The Iron Warriors were apparently intent on uncovering a Chaos Relic of some sort, so after defeating the Tallarn military, they began huge mining operations. At this point the Cadian military arrived in sector to assist the beleaugard defenders. Since no infantry were capable of living on the surface, the only available option of battle was that of tanks. The largest tank battle in the history of our species erupted on the surface of Tallarn, by the end of it, the Iron Warriors were defeated, and over a million wrecked tanks littered the sands.

Approximately twenty years after this, the official Tallarn Desert Raiders military force was formed. These regiments specialised in Desert fighting, and were highly adept at ambushing enemy forces in the desert.

The Tallarn Desert Raiders continued their attack on various enemy worlds until sometime around the 30th Millennium, when they were recalled after discovering the Relic the Iron Warriors were looking for. A powerful chaos relic, known as "The Crux" was discovered deep under the desert sands. Immediately after finding this relic both Eldar of the Biel-Tan craftworld and Iron Warriors spilled from the sky once more, to attempt to capture this relic. After months of fighting, the Eldar and Tallarn Desert Raiders formed an alliance to destroy the Chaos forces. After the defeat of the chaos forces, the Eldar and Imperials agreed to destroy the Crux.

With the loss of the Crux, the Iron Warriors halted there harassing of Tallarn. The Tallarn Desert Raiders continue assisting Imperial Guard regiments to this day.