Yes, quarks are considered to be fundamental particles according to the current understanding of particle physics. Quarks are elementary particles that are believed to be indivisible and have no substructure. They are the basic building blocks of matter and are thought to be the fundamental constituents of particles such as protons and neutrons.
There are six types of quarks known as flavors: up, down, charm, strange, top, and bottom. Quarks have fractional electric charges and combine together to form composite particles called hadrons, such as protons and neutrons. The interactions between quarks are described by the theory of quantum chromodynamics (QCD), which is a part of the standard model of particle physics.
Quarks have been extensively studied in particle accelerators, and their properties and behaviors have been observed and measured in various experiments, providing strong evidence for their fundamental nature.