She continued: "What if we chose not to fear but instead, to love. If that most delicate and vulnerable last flicker to the flame became another type of furnace entirely. Perhaps this will sound strange to some, romantic to others. To us: this is truth."
Bosworth went to on to say both her and Michael's hearts remained "full".
"We have never been so enamoured and deeply grateful for one another as we do in this decision to separate," she added.
Referencing their everlasting mutual respect and love for one another, Kate said: "We hold hands as tightly today as we entangled fingers on our wedding day. Our eyes look more deeply into one another, with more courage now.
"In the process of letting go, we have come to acknowledge that our love will never end. The connection does not simply disappear. The love deepens, the heart expands."
She finished the emotional post: "We believe the most epic love stories are those which transcend expectation. Our greatest honor has been to experience love like this, and to continue to marvel at the beauty of love’s evolution. What happens when we reach the end of something and realize … we are just at the beginning.
"This is love. And we will drink that down. Kate + Michael."
Kate and Michael began dating in 2011. A director, Michael met Kate on the set of Big Sur, which was subsequently released in 2013.
It was love at first sight for the pair, who were engaged and married by August 2013.
Speaking to InStyle UK at the time, Bosworth explained they barely even dated before they knew they were in it for the long haul.
"He said to me after just a few weeks, before we were even together, 'I'm going to marry you.' He just knew."