From the late 1990s, “cultural security” (al-amn al-thaqafi) or “thought security” (al-amn al-fikri) emerged as a major watchword in Saudi Arabia. This development could be evidenced from the exponential growth observed in the quantitative availability of academic works on the subject, many of which were produced under the rubric of “national security studies” (dirasat al-amn al-watani). This has been paralleled by the Saudi state’s embrace of thought security, particularly at the backdrop of its struggle against al-Qaeda in the Arabian Peninsula in the mid-2000s, through the formation of dedicated thought security institutions embedded within government bureaucracies and organizations. The concept of thought security refers to state-led securitization and management of an ideational (or cultural, thaqafi) sphere from external or internal threats which, if not effectively counteracted, could result in dangerous political, social, or economic consequences expressed in terms of “thought deviancy” (al-inhiraf al-fikri) resulting in societal implosion and state/regime collapse. The paper traces the historical evolution of thought security discourse. It argues that the origins of the discourse are rooted in the popularization of a holistic conception of culture by Arab intellectuals and revolutionary regimes in the 1950s and 1960s. This understanding of culture treats it as an ethnographic and territorialized category congruent with the nation-state, as being interlinked with political, economic and social conditions (consequently acting as an impediment or a catalyst for national modernization), and as being susceptible to the manipulation and subversion of foreign actors seeking to pursue their political, economic and military interests (al-ghazu al-thaqafi). At the core of this understanding is the notion of culture’s engineerability (bina al-thaqafa) by the state. This holistic conception of culture was imported into Saudi Arabia through Islamist networks in the context of the ‘Arab Cold war’, and consequently re-interpreted to fit an idiosyncratic framework whereby Islam came to denote culture. In the 1990s and 2000s, thought security institutions adopted this Islamized discourse on culture as their own, reproducing many of its key themes relevant (and not so relevant) to their securitization objectives. Since 2015, a new development – marked by the establishment of new thought security institutions and the re-structuring of the old – has played out and wherein the state, as part of its campaign to combat Islamist transnational threats such as the Muslim Brotherhood, has begun to ‘de-Islamize’ this discourse, ironically returning it “full circle”.