An unsubscribe link is crucial in email marketing for several reasons. Firstly, it is a legal requirement in many jurisdictions, such as the CAN-SPAM Act in the United States and the GDPR in the European Union. Secondly, it enhances the user experience by providing recipients with an easy way to opt out if they no longer wish to receive your emails. This helps maintain a positive relationship with your audience and can improve your email deliverability by reducing spam complaints.