Sōnosuke Nagashiro is a Japanese voice actor affiliated with the Osaka TV Talent Bureau. He is a graduate of the Amusement Media Academy and has a unique background, having trained as a chef before being discovered by the video game company SNK for his vocal abilities.

Nagashiro is best known for his long-standing association with the The King of Fighters franchise, where he has consistently voiced the character Ash Crimson. His first portrayal of the character was in the 2003 video game The King of Fighters 2003, a role he has reprised across numerous installments, including The King of Fighters XI, The King of Fighters XII, The King of Fighters XIII, The King of Fighters All Star, and The King of Fighters XV. In addition to the games, he also voiced Ash Crimson in the 2006 anime adaptation The King of Fighters: Another Day. His work on the character extends to related roles within the same franchise, such as providing the voices for Saiki and Evil Ash in The King of Fighters XIII.

Beyond his signature role as Ash Crimson, Nagashiro's other voice acting credits include the character Mitchie in the 2007 video game Doki Doki Akazukin and the role of Balrog in SNK vs. Capcom: SVC Chaos from 2003. His career is marked by a close and enduring collaboration with SNK, primarily centered on the King of Fighters series, where he has become the definitive voice for one of its central characters.