Essential oils have enjoyed great popularity from ancient times to today due to agreeable scent and widely known beneficial properties. As a result, nowadays they have become valuable natural ingredients in perfume and cosmetics, food and beverages, agricultural, pharmaceutical and other industries for employment in human health, agriculture and environment, representing potentially safer and more sustainable alternatives to synthetic substances. This Doctoral Thesis has been developed with the aim of corroborating that essential oils are safer and more sustainable alternatives to synthetic products used in the agri-food industry, and consequently promoting their use as “bio” products to maintain and improve the quality of crops and food, as well as human health and environment. It includes a compendium of scientific articles published in scientific journals indexed in Journal Citation Reports (JCR) and/or Scimago Journal Rank (SJR), positioned mainly in the first and second quartile, as well as other scientific articles indexed in different databases. It consists of a global summary with the main objectives, results and conclusions, followed by eight chapters that include the publications of this Doctoral Thesis. They are distributed on the one hand, in a section with the three articles published in the first quartile of SJR (Chapters 1-3), a second section (Chapters 4-7) with the other four accepted publications and a final chapter (unpublished data) with a comparative study about the phytotoxic effects of the commercial essential oils on food crops. Chapter 1 corroborates the previous in vitro phytotoxic activity of winter savory and peppermint essential oils by means of in vivo assays using a commercial emulsifiable concentrate including these essential oils, representing these products as a natural and environmental-friendly alternative to synthetic herbicides. Chapter 2 shows that turmeric essential oil represents a promising alternative in the control of both the invasive species Cortaderia selloana and weeds invading cucumber crops. Chapter 3 assigns lavender essential oil as an effective pre-emergent treatment for the control of Lolium multiflorum in cucumber crops. Chapter 4 specifies the differences in the chemical composition and phytotoxic activity between oregano, marjoram and Thymus mastichina essential oils, and the need to include information about their main compounds to standardize their activity. Chapter 5 demonstrates that tea tree and wintergreen essential oils can be useful in the control of the invasive species C. selloana and N. glauca, especially against the former that showed higher sensitivity to these essential oils. Chapter 6 details the phytotoxic activity of rosemary and basil essential oils with remarkable inhibition of the seedling length of weeds tested. Chapter 7 reports the post-emergent herbicidal effect of Eucalyptus globulus against Echinochloa crus-galli. Chapter 8 searches for the possible side effects derived from the application of bioherbicides on food crops.