This study aims to analyze the dynamics of cash liquidity fluctuations in the Libyan economy during the period 1990–2020 using Generalized Autoregressive Conditional Heteroskedasticity (GARCH) models. The research seeks to understand the volatile behavior of the money supply and its impact on monetary stability in a rentier economy characterized by political and economic uncertainty. The study employs quarterly data on money supply, the exchange rate of the Libyan dinar, and global crude oil prices, applying an advanced econometric methodology that includes unit root tests, ARCH-LM tests, and the GARCH(1,1) model. The results indicate the presence of volatility clustering in Libyan liquidity, with a significant positive effect of the exchange rate and a negative effect of oil prices on money supply. The study also confirms the model's efficiency in capturing volatility dynamics. The research provides recommendations for the Central Bank of Libya to improve liquidity management and enhance monetary stability in a volatile economic environment. Keywords: Liquidity Volatility, Cash Liquidity, Libyan Economy, GARCH Models.