Fiscal policy tools have piqued the interest of many governments and academics worldwide due to their ability to respond to aggregate demand shocks. Therefore, the thesis aims to identify the determinant factors of fiscal multipliers; examine the threshold level of the public debt that makes the fiscal policy sustainable, and identify the conditions under which countries undertake fiscal consolidation measures and the effects of fiscal consolidation on economic activity. In addition, this thesis deals with the connection between fiscal policy shocks, long-run fiscal sustainability, and contractionary fiscal policy, which most existing studies have largely failed to consider.Chapter two presents the definitions and concepts of expansionary and contractionary fiscal policy.In addition, this section reviews the terminologies, concepts, and debates surrounding the macroeconomic effects of fiscal policy on economic activity. Finally, chapter three discusses the overview of the trends in fiscal policy and economic performance of SSA countries from 2000-2019. It also highlights the effect of the COVID-19 pandemic on the economic performance and fiscal conditions of SSA countries.The thesis comprises three empirical chapters that are not mutually exclusive, yielding several novel and exciting results. The three chapters employ econometric panel techniques using annual data from 40 countries in SSA spanning from 2000 to 2019. The first study estimates the asymmetric effects of fiscal policy on output; the second assesses the tipping point of public debt to GD ratio that makes fiscal policy sustainable; and the third examines whether contractionary austerity works for SSA countries.Chapter four explores the output response to discretionary fiscal policy is a crucial aspect of examining various theories and findings of empirical studies and delivering guidance to policymakers. This study analyzes the output response to unanticipated fiscal spending shocks under several structural economic characteristic factors, including business cycle states, debt burden, the openness of the economy, exchange rate regimes, and institutional quality, using annual data from 40 countries in SSA spanning from 2000 to 2019 in a panel threshold vector autoregression model. The findings indicate that fiscal spending multipliers have sizable effects on output during recession periods; in economies operating under lower trade openness, a fixed exchange rate, a low debt burden, and a democratic governance regime. Based on the results, this ix xii