This repository presents the design and simulation of a fourth-order Butterworth low-pass filter with a cutoff frequency of 20 kHz using LTspice. Butterworth filters are renowned for their maximally flat frequency response in the passband, making them indispensable in applications requiring precise signal processing with minimal distortion. The design process involved selecting appropriate resistor and capacitor values to achieve the desired filter characteristics, ensuring a smooth transition between the passband and stopband while attenuating higher frequencies effectively. LTspice simulations were conducted to analyze the frequency response of the designed filter, including magnitude and phase characteristics, revealing its adherence to Butterworth filter principles. The simulated results demonstrate the filter's ability to effectively attenuate frequencies beyond the cutoff while preserving signal integrity within the passband. This study underscores the significance of Butterworth filters in signal processing applications and highlights the efficacy of LTspice in designing and analyzing analog filter circuits.