One of the key defining features of Westminster-type democracies is the acknowledgement of an official Opposition and a Leader of the Opposition typically referred to as a ‘prime minister in waiting’. This article focuses on this crucial element of Westminster democracy and applies a gender perspective, looking into women Leaders of the Opposition in the UK, Canada, New Zealand, and Australia (1975–2022). As this inquiry reveals, there have been few and mostly short-lived women Leaders of the Opposition. Further, contrary to plausible assumptions, there have been more women Leaders of the Opposition from conservative than from left-wing parties. In particular, however, the office of Leader of the Opposition has, with few exceptions, not proven as a springboard to the premiership. In fact, a majority of women prime ministers were ‘takeover prime ministers’, inheriting the office from a predecessor from their own party, rather than former Leaders of the Opposition, while many women Leaders of the Opposition were not even given the opportunity to lead their party into a national election campaign. The article discusses possible explanations for these patterns observed.