Future generations will be strongly affected by political decisions made today (e.g., by the long-term consequences of climate change). According to the democratic all-affected principle, the interests of everyone affected by political decisions should be considered in the political decision-making process. Future generations cannot influence democratic decision-making, since they do not yet exist. Election-based democratic incentive systems are said to make it difficult to consider the needs of future generations today. Surprisingly, however, since the early 1990s, an increasing number of democracies have established what could be called institutional proxy representatives of future generations (proxies), i.e., public bodies with institutionalized access to government and/or parliament that introduce the construed interests of future generations into the political decision-making process. Proxies help to consider future generations’ interests alongside the interests of current constituencies. After concept building, this comparative study searches all liberal democracies and identifies 25 proxies, with heterogeneous institutional designs. By employing membership criteria, three types are distinguished: (a) expertise-driven independent guardians (type I), (b) political or administrative advisory and coordination bodies (type II), and (c) sustainability stakeholder councils or committees (type III). They vary considerably in their formal capacity to influence political decision-making (i.e., on what legal basis they were provided with what instruments to address which phases of the policy process and which branches of government). Overall, they should not be overburdened with expectations. While they are usually equipped with the tools to voice the (construed) interests of future generations, they often lack the capacity to act as watchdogs with teeth when ignored.