The chapter discusses the development and challenges of optical quantum computing, highlighting the breakthrough in 2001 that demonstrated the feasibility of scalable quantum computing using single-photon sources, linear optical elements, and single-photon detectors. Despite initial scalability, the resource overhead was a significant practical challenge. Recent advancements, particularly in cluster states and error encoding, have significantly reduced this overhead, making all-optical quantum computing a viable option for large-scale quantum computers. Key challenges include achieving high-efficiency sources of indistinguishable single photons, low-loss scalable optical circuits, and high-efficiency single-photon detectors. The chapter also explores the use of single photons as qubits, the implementation of controlled-NOT (CNOT) gates, and the importance of fault tolerance. It reviews the progress in sources, detectors, and circuits, and discusses the potential of nonlinear and hybrid approaches. Despite significant progress, many technical hurdles remain, and the future prospects for optical quantum computing are promising but require further research and development.The chapter discusses the development and challenges of optical quantum computing, highlighting the breakthrough in 2001 that demonstrated the feasibility of scalable quantum computing using single-photon sources, linear optical elements, and single-photon detectors. Despite initial scalability, the resource overhead was a significant practical challenge. Recent advancements, particularly in cluster states and error encoding, have significantly reduced this overhead, making all-optical quantum computing a viable option for large-scale quantum computers. Key challenges include achieving high-efficiency sources of indistinguishable single photons, low-loss scalable optical circuits, and high-efficiency single-photon detectors. The chapter also explores the use of single photons as qubits, the implementation of controlled-NOT (CNOT) gates, and the importance of fault tolerance. It reviews the progress in sources, detectors, and circuits, and discusses the potential of nonlinear and hybrid approaches. Despite significant progress, many technical hurdles remain, and the future prospects for optical quantum computing are promising but require further research and development.