德摩斯梯尼（Δημοσθένης，前384年－前322年），也译作狄摩西尼或德摩斯提尼，古希腊著名的演说家，民主派政治家。

早年从伊萨攸（Isaeus）学习修辞，旋教授修辞学。继而从事政治活动，极力反对马其顿入侵希腊，发表《斥腓力》(Philippics)等演说，谴责马其顿王腓力二世的扩张野心。喀罗尼亚战役（前338年）后亡命海外，公元前323年马其顿亚历山大死，返回雅典组织反马其顿运动，失败后自杀。

Demosthenes (/dɪˈmɒs.θəniːz/; Greek:Δημοσθένης Dēmosthénēs [dɛːmostʰénɛːs]; 384–322 BC) was a prominent Greek statesman and orator of ancient Athens. His orations constitute a significant expression of contemporary Athenian intellectual prowess and provide an insight into the politics and culture of ancient Greece during the 4th century BC. Demosthenes learned rhetoric by studying the speeches of previous great orators. He delivered his first judicial speeches at the age of 20, in which he argued effectively to gain from his guardians what was left of his inheritance. For a time, Demosthenes made his living as a professional speech-writer (logographer) and a lawyer, writing speeches for use in private legal suits.