This study explored two aspects of K-12 core content area teachers' experiences with digital citizenship through the Connectivism lens (Siemens, 2005). First, it explored how teachers instruct students on digital citizenship topics, including how they define digital citizenship and integrate it into their core content area curriculum. Second, it examined teachers' experiences and needs regarding digital citizenship professional development. This study followed a basic qualitative approach and used interviews with a follow-up questionnaire to gather data. Participants' responses were analyzed using Fereday and Muir-Cochrane's (2006) six-step, hybrid approach of inductive and deductive coding and theme development. Findings and discussion were presented through the learning theory of Connectivism. Information on how core content area teachers define digital citizenship was summarized using the S3 Guiding Principles from Ribble and Park (2019). Information on teachers' experiences integrating digital citizenship into their core content curriculum revealed five major themes: Responsibility, Student Behavior, News & Media Literacy, Non-Cognitive Competencies, and Technology Use. Findings related to professional development experiences were presented through five broad themes: Personal Learning Networks, Parenting & Family, Self-Exploration, Technology Facilitators & Other Technology Champions, and Participating in the Digital World. Findings related to teachers' professional development needs regarding integrating digital citizenship into their core content curriculum were summarized through three themes: making this content relevant and authentic for their students, raising awareness among their peers to build a community around teaching digital citizenship, and identifying resources to integrate this subject matter into their curricula. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]