This article introduces a new measure of a firm's negative impact on biodiversity, the corporate biodiversity footprint (CBF), and studies whether it is priced in an international sample of stocks. On average, the CBF does not explain the cross-section of returns between 2019 and 2022. However, a biodiversity footprint premium (higher returns for firms with larger footprints) began emerging in October 2021 after the Kunming Declaration, which capped the first part of the UN Biodiversity Conference (COP15). Consistent with this finding, stocks with large footprints lost value in the days after the Kunming Declaration. The launch of the Taskforce on Nature-related Financial Disclosures (TNFD) in June 2021 had a similar effect. These results indicate that investors have started to require a risk premium upon the prospect of, and uncertainty about, future regulation or litigation to preserve biodiversity. The CBF aggregates the biodiversity loss caused by a firm's annual activities related to land use, greenhouse gas (GHG) emissions, water pollution, and air pollution. It expresses this loss in terms of km².MSA and quantifies not only the direct impact of a firm but also the biodiversity loss along the entire value chain. The CBF contains scope 1, 2, and 3 components. Our international sample consists of 2,106 listed firms from 34 countries for which CBF data are available from IDL over the years 2018–2021. While the sample period includes only a few years, the most important global policy developments concerning biodiversity are also quite recent. Retail and Wholesale, Paper and Forest, and Food are the sectors with the largest average CBF, reflecting these sectors' intensive land use or contribution to air pollution. The CBF correlates with whether firms are targeted by the investor coalition Nature Action 100 (NA100), which, in June 2023, released a list of 100 firms to engage with to tackle biodiversity and nature loss. Almost 70 percent of NA100 targets are located in the top quintile of the CBF distribution. Using textual analysis, we find that terms related to biodiversity are mentioned in only 5.0 percent of our sample firms' earnings calls. This low number is consistent with Giglio et al. (2023), who find that only 3.8 percent of U.S. firms' 10-K statements mention biodiversity terms. As a result, the correlation between the CBF and the number of biodiversity terms in earnings calls is just 8.8 percent. How can a firm’s CBF be expected to correlate with its stock returns? A first possibility is that large-CBF stocks will earn higher returns, as these firms potentially face higher transition risks. These transition risks may result from legal fines or the costsThis article introduces a new measure of a firm's negative impact on biodiversity, the corporate biodiversity footprint (CBF), and studies whether it is priced in an international sample of stocks. On average, the CBF does not explain the cross-section of returns between 2019 and 2022. However, a biodiversity footprint premium (higher returns for firms with larger footprints) began emerging in October 2021 after the Kunming Declaration, which capped the first part of the UN Biodiversity Conference (COP15). Consistent with this finding, stocks with large footprints lost value in the days after the Kunming Declaration. The launch of the Taskforce on Nature-related Financial Disclosures (TNFD) in June 2021 had a similar effect. These results indicate that investors have started to require a risk premium upon the prospect of, and uncertainty about, future regulation or litigation to preserve biodiversity. The CBF aggregates the biodiversity loss caused by a firm's annual activities related to land use, greenhouse gas (GHG) emissions, water pollution, and air pollution. It expresses this loss in terms of km².MSA and quantifies not only the direct impact of a firm but also the biodiversity loss along the entire value chain. The CBF contains scope 1, 2, and 3 components. Our international sample consists of 2,106 listed firms from 34 countries for which CBF data are available from IDL over the years 2018–2021. While the sample period includes only a few years, the most important global policy developments concerning biodiversity are also quite recent. Retail and Wholesale, Paper and Forest, and Food are the sectors with the largest average CBF, reflecting these sectors' intensive land use or contribution to air pollution. The CBF correlates with whether firms are targeted by the investor coalition Nature Action 100 (NA100), which, in June 2023, released a list of 100 firms to engage with to tackle biodiversity and nature loss. Almost 70 percent of NA100 targets are located in the top quintile of the CBF distribution. Using textual analysis, we find that terms related to biodiversity are mentioned in only 5.0 percent of our sample firms' earnings calls. This low number is consistent with Giglio et al. (2023), who find that only 3.8 percent of U.S. firms' 10-K statements mention biodiversity terms. As a result, the correlation between the CBF and the number of biodiversity terms in earnings calls is just 8.8 percent. How can a firm’s CBF be expected to correlate with its stock returns? A first possibility is that large-CBF stocks will earn higher returns, as these firms potentially face higher transition risks. These transition risks may result from legal fines or the costs