Annabel Goldie said she will stay on until a likely election to find a new leader later this year. Her decision means that Alex Salmond will face three new party leaders at Holyrood, all vying to oppose the first SNP majority Scottish Government.
Miss Goldie said: "I believe that the time has come for the torch to pass and I can confirm that I will not be a candidate. There are four years until the next UK general election, and five years until the next Holyrood contest.
"I want my successor to have the maximum time for him or her to shape the party and its policies, and to lead the opposition at Holyrood. For the sake of clarity, I will remain as leader of the MSP group until my successor takes over, and I will of course remain as an MSP for the duration of the Parliament.
The election, which saw Alex Salmond's SNP secure the Parliament's first ever majority, marked the Tories worst electoral performance at Holyrood.
In 2007 the party secured 17 seats, although under new boundaries they notionally had 20 seats.
Following Thursday's vote, the party's number of seats dropped to 15.
Speaking in Edinburgh, Ms Goldie said: "The Scottish election result was seismic.
"Nobody, not even Alex Salmond, thought that the SNP would win an overall majority at Holyrood.
I believe that the time has come for the torch to pass and I can confirm that I will not be a candidate. There are four years until the next UK General Election, and five years until the next Holyrood contest. I want my successor to have the maximum time for him or her to shape the Party and its policies and to lead the opposition at Holyrood.
“For the sake of clarity, I will remain as leader of the MSP group until my successor takes over, and I will of course remain as an MSP for the duration of the Parliament.
“It has been an enormous privilege to lead my party. Over the coming weeks, months and years I will fight with every ounce of my energy to support my party, my successor and my country.
