Mobile devices have drawn a new path in learning through the transformation from traditional classroom education to learning outside the classroom at any time and any place. The great features of mobile phones, which are wide spread among people and are taken with them wherever they go, have been contributed by many researchers of exploit the advantages to producing a variety of mobile learning systems for different types of knowledge. This including second languages, especially the English language. The main aim of this book is to explain how mobile devices can be used to learn English as a second language, to improve the efficiency of the English skills of the learners. Because, English is the most common language spoken in the world, for this, knowing the English language for non-native speakers has become so crucial. Mobile-based learning or mobile learning can support different kinds of learning including language. By using mobile devices to learn English as a second language, learning gains great applause because it makes the language learning process more effective, interesting and enjoyable and presents solutions to some problems faced by learners during learning.