在英语中，李先生可以称为"Mr. Lee"。来源："Mr."是英语中用来对男性称呼的尊称，表示敬意。"Lee"是李先生的姓氏。

例句：

"Mr. Lee is a very respected member of our community." (李先生是我们社区里非常受尊敬的成员。)

"I would like to introduce you to Mr. Lee. He is the CEO of our company." (我想向你介绍李先生。他是我们公司的首席执行官。)

"Mr. Lee has been invited to give a speech at the conference." (李先生已被邀请在会议上发表演讲。)