8:55 AM PT -- NPH just tweeted ... strongly DENYING he dropped the N-word.
"I would NEVER be so disrespectful," he wrote.
So what DID Neil say? Still unclear.
Neil Patrick Harris opened the Tony Awards by bringing Mike Tyson out on stage and dropping the N-WORD right in Tyson's face ... or at least that's how it sounds.
Tyson joined NPH while he was singing a song where he repeated the lyric ... "we're going bigger" -- but about 10 seconds after Tyson came out ... NPH sang something that sounds A LOT like the n-word.
So, we've gotta ask ...