Michael Phelps -- 'I'm Deeply Sorry' ... For DUI Arrest

Michael Phelps just issued a statement on his DUI arrest in Baltimore this morning ... saying he takes "full responsibility" and is sorry he let everyone down.

Here's the statement Phelps just issued on Twitter:

"Earlier this morning, I was arrested and charged with DUI, excessive speeding and crossing double lane lines."

"I understand the severity of my actions and take full responsibility."

"I know these words may not mean much right now but I am deeply sorry to everyone I have let down."

TMZ Sports broke the story ... Phelps was pulled over around 1:40 AM for going 84 in a 45 ... and during the stop, the officer noticed the Olympic legend was hammered.

He was charged with DUI, excessive speeding and crossing double lanes.