The paper expands the conceptual framework within which we examine mortgage debt by reconceptualising mortgages as a biotechnology: a technology of power over life that forges an intimate relationship between global financial markets, everyday life and human labour. Taking seriously the materiality of mortgage contracts as a means of forging new embodied practices of financialisation, we urge for the need to move beyond a policy‐ and macroeconomics‐based analysis of housing financialisation. We argue that more attention needs to be paid to how funnelling land‐related capital flows goes hand in hand with signing off significant parts of future labour, decisionmaking capacity and well‐being to mortgage debt repayments. The paper offers two key insights. First, it exemplifies how macroeconomic and policy changes could not have led to the financialisation of housing markets without a parallel biopolitical process that mobilised mortgage contracts to integrate the social reproduction of the workforce into speculative global real‐estate practices. Second, it expands the framework of analysis of emerging literature on financialisation and subjectification. Focusing on the mortgage defaults and evictions crisis in Spain, we document how during Spain's 1997–2007 real‐estate boom the promise of mortgages as a means to optimise income and wealth enrolled livelihoods into cycles of global financial and real‐estate speculation, as home security and future wealth became directly dependent on the fluctuations of financial products, interest rates and capital accumulation strategies rooted in the built environment. When, after 2008 unemployment escalated and housing prices collapsed, mortgages became a punitive technology that led to at least 500 000 foreclosures and over 250 000 evictions in Spain.