The actress was promoting the sixth season of her TV hit Girls, when a shock question appeared to leave the 61-year-old speechless and in a panic.
The presenter blamed being of a different generation for her confusion, which saw the interview awkwardly cut short.
"Lena Dunham, thank you so much for stopping by. I had a chance to look at three shows for this new season – it looks terrific," Maria had started.
The 30-year-old quickly replied: "You saw a penis, right?" hinting at the regular nudity in the comedy/drama.
Lena Dunham interview with Maria Shriver on the Today show went far from to plan earlier
Lena Dunham left Maria Shriver flustered after asking a penis question
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That's the difference between generations, I wasn't brought up talking like that!
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Mumbling and looking uncomfortable, Maria tried to continue: "Yeah… I saw more than that… You caught me there for a second.
"I'm not sure if you're allowed to say that on television. But you did…" she said looking around.
Joking about her language, Lena laughed: "I won't be coming back. I'm going out with a bang."
Maria Shriver was left asking for help from her co-stars
Lena Dunham apologised to the host for her question
Maria then told viewers: "We're just going out… What did it matter… Help! She just threw me off! That's the difference between generations, I wasn't brought up talking like that.
"I'm so sorry! You said, 'Penis!' Thanks so much for having me," Lena, who was sporting a patterned minidress, apologised.
"Oh we're still on the air, sit down! Matt, are you supposed to be saying something?" Maria added, addressing her co-star.
Girls season six begins Monday at 10pm on Sky Atlantic.