Lindsey Vonn -- Tailing Tiger Woods ... at The Masters

Might as well tailor that green jacket for Tiger Woods ... 'cause his 5'10" blonde good luck piece -- aka Lindsey Vonn -- showed up for round one of The Masters.

LV turned up at Augusta National to support her man wearing a giant floppy hat ... perhaps to make sure cameras can find her all day while she follows Tiger?

We're betting Tiger doesn't care what she wears 'cause he's been on a tear since going public about banging Lindsey -- winning two tournaments in a row, and 3 out of his last 5.