This chapter presents new, annotated translations of various surviving works by Markianos of Herakleia, who is probably the man of that name who lectured at Constantinople just before and just after AD 400. The chapter introduction shows that it is to him that we owe one of the two collections of geographical works that survive from antiquity (perhaps built on foundations laid by Menippos); its sole surviving copy, though incomplete, includes several works translated in the present volume. The main work presented here is the partly extant abridgement of Markianos’ Circumnavigation of the Outer Ocean, dealing first (book 1) with the lands from eastern Africa to western China, and then (book 2) with the coasts of the northern Atlantic. To this are appended over 40 citations of Markianos by Stephanos of Byzantion and others, as well as the theoretical opening sections of Markianos’ epitome (précis) of Menippos (the whole epitome is in Chapter 21 of this volume). His perceptive preface to Ps.-Skylax is printed in Chapter 7. At many points, such as when discussing how to present distances that display systematic errors, he shows himself to be one of the most self-aware and methodologically astute of ancient writers, as well as exceptionally widely read. New maps explain his presentation of the Far East and northern Europe.