The Welsh Underground Network (WUN) is a prominent Marxist-Leninist organization dedicated to establishing a Welsh Socialist Republic through active community engagement. Founded in 2019, WUN emerged from the radical news service Valleys Underground, evolving into a dynamic movement committed to grassroots action across Wales. At its core, WUN believes that genuine change must stem from tangible deeds and has mobilized efforts ranging from historical commemorations to addressing local issues like landfill campaigning and supporting foodbanks.

Symbolized by a distinctive flag representing the rich history of Welsh working-class struggle, WUN unites socialists under a common cause. Their initiatives extend to actions such as restoring significant local heritage sites and organizing community clean-up events. With chapters in various cities including Wrexham and Swansea, the Welsh Underground Network continues to grow, inviting others to join their mission in creating a more equitable society for all. Through education, activism, and community service, WUN strives to inspire a collective movement for social justice in Wales.