第一代新凯恩斯主义经济学（英语：Neo-Keynesian economics）又译为新凯恩斯学派，是20世纪30年代到70年代间，特别是二战结束之后到20世纪70年代间从凯恩斯主义经济学中发展起来的一种宏观经济学思想。它的主要的代表人物是保罗·萨缪尔森、弗兰科·莫迪利安尼、约翰·希克斯、詹姆士·托宾等。

第一代新凯恩斯主义经济学的一个重要的子学派为新古典综合学派，该学派由约翰·希克斯与保罗·萨缪尔森创立。他们将第一代新古典主义经济学的数学分析方法引进凯恩斯经济学中，充实了它的内容，之后形成新凯恩斯学派。

Neo-Keynesian economics is a school of macroeconomic thought that was developed in the post-war period from the writings of John Maynard Keynes. A group of economists (notably John Hicks, Franco Modigliani, and Paul Samuelson), attempted to interpret and formalize Keynes' writings, and to synthesize it with the neo-classical models of economics. Their work has become known as the neo-classical synthesis, and created the models that formed the core ideas of neo-Keynesian economics. These ideas dominated mainstream economics in the post-war period, and formed the mainstream of macroeconomic thought in the 1950s, 1960s and 1970s.