This　research　work　is　focused　on　the　nonlinear　modeling　and　control　of　a　hydrostatic　thrust　bearing.　In　the　proposed　work,　a　mathematical　model　is　formulated　for　a　hydrostatic　thrust　bearing　system　that　includes　the　effects　of　uncertainties,　unmodelled　dynamics,　and　nonlinearities.　Depending　on　the　type　of　inputs,　the　mathematical　model　is　divided　into　three　subsystems.　Each　subsystem　has　the　same　output,　i.e.,　fluid　film　thickness　with　different　types　of　input,　i.e.,　viscosity,　supply　pressure,　and　recess　pressure.　An　extended　state　observer　is　proposed　to　estimate　the　unavailable　states.　A　backstepping　control　technique　is　presented　to　achieve　the　desired　tracking　performance　and　stabilize　the　closed-loop　dynamics.　The　proposed　control　technique　is　based　on　the　Lyapunov　stability　theorem.　Moreover,　particle　swarm　optimization　is　used　to　search　for　the　best　tuning　parameters　for　the　backstepping　controller　and　extended　state　observer.　The　effectiveness　of　the　proposed　method　is　verified　using　numerical　simulations.