Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 14, 2019
Entity Registrant Name	RMG Acquisition Corp.
Entity Central Index Key	0001757932
Trading Symbol	rmgun
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Class A Common stock
Entity Common Stock, Shares Outstanding		23,000,000
Class B common stock
Entity Common Stock, Shares Outstanding		5,750,000