I recently facilitated a workshop on Facilitation Skills and all the attendees had one question they wanted answered, “How do I manage someone who dominates all conversations?”
This is a really interesting question, and a very real fear for anyone facilitating a group. In this case, the person was aware they dominated the conversations and put it down to being passionate about the subject.
Unfortunately, other participants in the group felt unheard, spoken over, not important, fearful of speaking up, fearful of being in conflict with this person, and ultimately reluctant to attend meetings with them present.
Some tips we came up with were:
Before the session, acknowledge the person’s passion and explain that their input makes others feel reluctant or unable to give their opinion or input, and come up with an inconspicuous signal to remind them to let others speak. This could be walking to a particular space in the room or taking a drink from a specific-coloured mug.
Rather than have everyone speak, ask the group to write down their ideas or thoughts on a post-it or in the online chat. This enables them to have their say and the facilitator can raise their responses.
Call on other people to respond to a question as you ask it. For example, “Chris, what do you think went well during the last session?”, just be sure not to call on the quietest person first.

Further tips that can help if the person is unaware of their actions:
Set an agenda with time allocations and stick to it.
Set the ground rules at the beginning.
Speak to the person privately and let them know how their behaviour is impacting the meeting.
If the meeting is seeking input or ideas, ask attendees to do some pre-work and gather some of the information prior to the meeting.
As they indicate they wish to speak, you can say 'I would like to hear from a couple other people first, and then I will come back to you Chris'.
But consider why they are over-talking. Are they nervous, trying to impress someone, sitting next to someone who enables them, unaware of social cues, hyperactive, unable to hear when others start speaking, or just love to hear the sound of their own voice? If you can find the reason, it can help you find the best solution.