A cutting element comprises a supporting substrate, and a cutting table attached to an end of the supporting substrate. The cutting table comprises a first region and a second region. The first region comprising inter-bonded diamond particles and is substantially free of at least highly catalytic metallic compounds, one or more non-catalytic compounds within interstitial spaces between the inter-bonded diamond particles, and voids within interstitial spaces between the inter-bonded diamond particles. The second region comprising inter-bonded diamond particles, one or more non-catalytic compounds within interstitial spaces between the inter-bonded diamond particles, and one or more metallic phases within interstitial spaces between the inter-bonded diamond particles. The first region of the cutting table has a content of elemental metal of at least about 2.6 wt %. A method of forming a cutting element, and an earth-boring tool are also described.