Abstract Citizen science, and online citizen science, are part of a movement towards open and participatory science, where education is particularly interested due to its potential benefits such as educating learners about the scientific process, as well as the topics of their study. This research is part of a project investigating the role of online citizen science in primary school science education, and provides an understanding of both citizen science and online citizen science from the literature, and then derives working definitions, which will be the guide for our further investigations.IntroductionThere has been a movement in recent years towards open and participatory science, in an effort to make scientific research more accessible to all levels of society. Citizen science (CS), and online citizen science (OCS) aim to help with this movement \citep{Bonney_2009}, where the latter has become more and more popular in recent years \citep{Nov2011}. One area of society that has become particularly interested in OCS is that of education (especially science education) \citep{wynne2017}, where potential benefits are to use OCS to educate learners about the scientific process, and about the particular topics of real scientific projects through participation facilitated by digital technologies. However, research on how OCS relates to the formal setting of science education has received little attention so far. Furthermore, while much research spoke about OCS, no work so far seems to offer an unambiguous differentiation between CS and OCS. This article aims to close this gap, first providing an understanding of both CS and OCS from the literature, and then deriving working definitions from these understandings, which will be the guide for our investigation of online citizen science in the science education of primary school children.The remainder of this article is structured as follows. We begin by providing the background of our research project, emphasising the link to education research and teaching practice. Afterwards we describe the methodology we followed for our initial literature review from which we derived the working definitions of CS and OCS, which will be presented afterwards. Finally we give a brief outline of how this informs our ongoing research on novel ways to purposefully embed OCS for Year 3-8 students in New Zealand primary classrooms that meet the aims and intentions of the Nature of Science strand of the New Zealand Curriculum.Citizen Scientists in the Classroom: Investigating the Role of Online Citizen Science in Primary School Science Education This research is part of a larger research project that has been funded by the Teaching and Learning Research Initiative (TLRI). The TLRI is a fund initiated by the New Zealand government to "link education research and teaching practice"\cite{site}. The "Citizen Scientists in the Classroom" project explores the impact on student learning and engagement with science, incorporating OCS projects in New Zealand primary school classrooms (Year 3-8). It involves a co-constructive partnership (see Fig. 1)  between researchers at Victoria University of Wellington and primary school teachers who have been identified as advocates of science education in New Zealand, and is the first attempt to investigate the potential of OCS projects to contribute to the improvement of science education of primary-age children.