\documentclass[12pt,a4paper,openany]{book}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{lipsum}
%%%%%%%%%%%%%%%%%%%
\usepackage{fancyhdr}
\pagestyle{fancy}
\begin{document}
\tableofcontents
\chapter*{Introduction}
\lipsum
\chapter{one}
\chapter{two}
\chapter{three}
\chapter{four}
\end{document}
i want to obtain automatically Introduction instead of contents
Thank you
\markbothas also explained here: Chapter name in the header with \chapter* – leandriis Nov 01 '20 at 09:57