Liquefied natural gas (LNG) is attracting great interest as a clean energy alternative to other fossil fuels, mainly due to its ease of transport and low carbon dioxide emissions, a primary factor in air pollution and global warming. It is expected that this trend in the use of LNG will lead to steady increases in demand over the next few decades. To meet the growing demand for LNG, natural gas liquefaction plants have been constructed across the globe. Furthermore, single train capacity has been increased to strengthen price competitiveness. To achieve greater capacity, more complex refrigeration cycle designs that combine two or more different conventional single refrigeration cycles are being developed to obtain synergistic effects in the liquefaction process. At the same time, a variety of recent studies have focused on designing suitable processes for offshore and small-scale plants to improve the profitability of stranded gas fields. LNG plants are known to be energy/cost-intensive, as they require a large amount of power for the processes of compression and refrigeration, and need special equipment such as cryogenic heat exchangers, compressors, and drivers. Therefore, one of the primary challenges in the LNG industry is to improve the efficiency of the current natural gas liquefaction processes in combination with cost savings. In this paper, we review recent developments in LNG processes, with an emphasis on commercially available refrigeration cycles. We also discuss recent research and suggest future directions for natural gas liquefaction processes. Up to this point, most studies have focused on operating cost. To achieve better results, future studies that investigate optimal design and operation of LNG technologies should consider both capital cost and operating cost.