The legislative 'power of the purse' is an important constitutional principle across contemporary democracies. Yet, national legislatures differ in their approach to fiscal control. What is the role of legislatures in the budget process? Why does this role vary across democratic countries? Are powerful assemblies a threat to the prudent management of public finances? This unprecedented survey of legislative budgeting tackles these questions using quantitative data and case studies. The analysis reveals a striking variation in the budgetary role of national legislatures across contemporary democracies, which is influenced by colonial heritage as well as current political dynamics. It also finds consistent evidence that powerful legislatures are associated with higher public spending than those with limited authority. Based on in-depth accounts of fundamental reforms to the budget process in Sweden and South Africa, Legislatures and the Budget Process explores how the tension between legislative authority and fiscal discipline might be reconciled.