Summary: This dataset contains electroencephalographic (EEG) recordings of 44 subjects playing in pair to the multi-user version of a visual P300 Brain-Computer Interface (BCI) named Brain Invaders. The interface uses the oddball paradigm on a grid of 36 symbols (1 or 2 Target, 35 or 34 Non-Target) that are flashed pseudo-randomly to elicit the P300 response. EEG data were recorded using 32 active wet electrodes per subjects (total: 64 electrodes) during four randomised conditions (Cooperation 1-Target, Cooperation 2-Targets, Competition 1-Target, Competition 2-Targets). The experiment took place at GIPSA-lab, Grenoble, France, in 2015. A full description of the experiment is available at https://hal.archives-ouvertes.fr/hal-02173913. Python code for manipulating the data is available at https://github.com/plcrodrigues/py.BI.EEG.2015b-GIPSA. The ID of this dataset is bi2015b. Full description of the experiment and dataset: https://hal.archives-ouvertes.fr/hal-02173913 Investigators: Eng. Louis Korczowski, B. Sc. Martine Cederhout Technical Support: Eng. Anton Andreev, Eng. Grégoire Cattan, Eng. Pedro. L. C. Rodrigues, M. Sc. Violette Gautheret Scientific Supervisor: Ph.D. Marco Congedo ID of the dataset: bi2015b