If it's in the middle of a sentence, you don't capitalize 'the'. But as for the others- President- proper noun, capitalized of- preposition, not capitalized the- article, not capitalized United States- object of the preposition, proper noun, capitalized. so yes, it's proper to say 'the President of the United States'. :)

Avatar, You are asking both about capitalization rules and the use of the definite article with official titles, I assume. The use of the article with titles. -In the case of official job titles, "the" can be dropped if there is only ONE such person holding the title at any given time. Barrack Obama is President of the United States Elizabeth is Queen of England. or Barrack Obama is the president of the United States. The rules for capitalization are much more complicated. There are different rules for newspapers, and government publications, so in many cases it is a question of style. The trend in the U.S. is towards “less” capitalization. -High-ranking government officials' titles are CAPITALIZED when the title comes first before the name: The President of the United States, Barack Obama, left on an official visit to Thailand. President of the United States Barack Obama today visited a manufacturing plant in Chicago. -After a signature: Yours sincerely, Barrack Obama, President of the United States -If you omit the article with the title: Barrack Obama is President of the United States -Do NOT capitalize when speaking generally about the president or using the title instead of the name. Barack Obama is the current president of the United States but he will not be the president of the United States in 2012. The president of the United States will be at the dinner. -When the title comes after the name don’t capitalize. Barack Obama, president of the United States, is the first black man ever elected to that high office. Barrack Obama is the president of the United States. -If you want to emphasize the high dignity of the office you can capitalize as a matter of style. Barrack Obama is the President of the United States. The people elect the President of the United States. The President of the United States just stepped off the plane! *White House communications commonly capitalize President, Vice-President, and First Lady in all cases.

孙悟空也学英语了哈哈。

"The President Of The United States' sounds much more natural to me.

It is correct to say the President of the United States. (The word President is captialized when referring to the President of the USA.) I hope this helps! Have a great day!