Ashwagandha
Ashwangandha is an evergreen shrub that grows in Asia and Africa and it's commonly used for stress-coping. It also reduces the activity of the hypothalamic-pituitary-adrenal (HPA) axis which is a system in the body that regulate the stress response.
In a small study with 58 participants, those that took 250 or 600mg of Ashwaganda extract for 8 weeks straight had significantly reduced perceived stress and levels of the stress hromone cortisol compared to those who didn't. In addition, those that took this herb also showed improvements in sleep quality.