"I will not be seeking any political after my term ends," she told a new conference.
Her CDU party was severely weakened in elections in the state of Hesse on Sunday, the latest poor performance by parties in her coalition government.
She also said she would stand down as CDU leader in the coming days. She has held the post since 2000.
She said she took "full responsibility" for recent election setbacks.
In Hesse, both her centre-right CDU and its coalition partners, the Social Democrats, were 10% down on the previous poll there - even though they remain in power.