Patrick Harvie has announced he will step down as co-leader of the Scottish Greens party after nearly 17 years.
The Glasgow MSP announced on Wednesday that he will not stand in the party's upcoming leadership election which is set to take place this summer.
He intends to seek re-election as an MSP at next year's Scottish Parliament election and will remain in post until his party elects a new leader.
The former Scottish government minister said it has been an "extraordinary privilege" to lead the Greens.
He told BBC Scotland News: "With a new election coming up and with myself having been in the equivalent of the co-leader role for honestly a ridiculously long time now, I think the right time is now for a new face to join the leadership team."
In a statement, Harvie said that when he was first elected to Holyrood in 2003 "few people regarded the Greens as a serious political force".
He added that the party had since become "the most significant, sustained new movement in Scottish politics for generations".