| Classroom, Inc.EIN 13-3666846 | Education | NY | $4,643,853Mid-sized | 87.65 |
| Clean Air Task ForceEIN 04-3512550 | Research and Public Policy | MA | $5,368,687Mid-sized | 93.52 |
| Clean Ocean ActionEIN 22-2897204 | Environment | NJ | $581,461Small | 92.82 |
| Clean Water FundEIN 52-1043444 | Environment | DC | $5,390,587Mid-sized | 90.03 |
| Clean WisconsinEIN 39-1413448 | Environment | WI | $1,905,696Small | 89.72 |
| Clear Horizons AcademyEIN 20-2697232 | Education | UT | $622,733Small | 69.34 |
| Clearwater Camp FoundationEIN 43-2024465 | Human Services | WI | $890,698Small | 86.95 |
| Clearwater Free ClinicEIN 59-1852871 | Health | FL | $3,222,946Small | 92.22 |
| Clearwater Marine AquariumEIN 59-2086737 | Animals | FL | $15,652,675Large | 95.87 |
| Cleveland Animal Protective LeagueEIN 34-0714644 | Animals | OH | $5,028,954Mid-sized | 90.02 |
| Cleveland Botanical GardenEIN 34-0239538 | Environment | OH | $7,054,254Mid-sized | 72.19 |
| Cleveland International Film FestivalEIN 34-1262368 | Arts, Culture, Humanities | OH | $3,287,755Small | 93.55 |
| Cleveland Leadership CenterEIN 34-1927317 | Education | OH | $1,646,527Small | 86.32 |
| Cleveland Museum of Natural HistoryEIN 34-0714338 | Arts, Culture, Humanities | OH | $18,722,320Large | 90.29 |
| Cleveland Public TheatreEIN 34-1359225 | Arts, Culture, Humanities | OH | $2,140,830Small | 92.22 |
| Cleveland Sight CenterEIN 34-0714652 | Human Services | OH | $10,147,874Mid-sized | 94.07 |
| Climate CentralEIN 26-1797336 | Environment | NJ | $9,872,125Mid-sized | 84.53 |
| Climate SolutionsEIN 91-1123302 | Environment | WA | $3,134,433Small | 82.66 |
| Clinic for the Rehabilitation of WildlifeEIN 23-7271040 | Animals | FL | $1,469,633Small | 88.36 |
| Clothes To KidsEIN 14-1849798 | Human Services | FL | $1,221,078Small | 91.27 |
| COA Youth & Family CentersEIN 39-0806339 | Human Services | WI | $7,224,306Mid-sized | 98.69 |
| Coachella Valley Rescue MissionEIN 95-2684844 | Human Services | CA | $7,269,992Mid-sized | 96.83 |
| Coaching CorpsEIN 94-3310845 | Human Services | CA | $4,311,471Mid-sized | 90.46 |
| Coalition Against Trafficking in WomenEIN 22-3032134 | International | NY | $720,237Small | 82.48 |
| Coalition for Christian OutreachEIN 25-1216330 | Religion | PA | $12,058,281Mid-sized | 95.67 |
| Coalition for Clean AirEIN 23-7120567 | Environment | CA | $1,050,597Small | 85.15 |
| Coalition for Engaged EducationEIN 95-4515019 | Education | CA | $1,278,892Small | 79.09 |
| Coalition for the HomelessEIN 13-3072967 | Human Services | NY | $11,680,807Mid-sized | 89.70 |
| Coalition for the Homeless of Central FloridaEIN 59-2814255 | Human Services | FL | $5,987,495Mid-sized | 91.40 |
| Coalition on Temporary ShelterEIN 38-2420565 | Human Services | MI | $8,585,803Mid-sized | 89.88 |
| Coalition to Abolish Slavery & Trafficking (CAST)EIN 10-0008533 | Human Services | CA | $3,782,163Mid-sized | 90.07 |
| Coalition to Restore Coastal LouisianaEIN 72-1115589 | Environment | LA | $2,240,672Small | 85.48 |
| Coalition to Salute America's HeroesEIN 52-1351773 | Human Services | VA | $12,071,141Mid-sized | 70.20 |
| Coast Guard FoundationEIN 04-2899862 | Human Services | CT | $6,525,302Mid-sized | 83.53 |
| Coast Guard Mutual AssistanceEIN 31-1801931 | Human Services | VA | $3,792,602Mid-sized | 93.15 |
| Coastal Bend Food Bank EIN 74-2234089 | Human Services | TX | $16,183,493Large | 88.35 |
| Coastal Conservation AssociationEIN 74-1984482 | Environment | TX | $13,776,533Large | 81.37 |
| Coastal Conservation LeagueEIN 57-0887278 | Environment | SC | $3,691,863Mid-sized | 91.84 |
| Coastal Maine Botanical GardensEIN 01-0476545 | Environment | ME | $4,847,073Mid-sized | 85.71 |
| Coburn Place Safe HavenEIN 37-1421922 | Human Services | IN | $1,762,647Small | 79.43 |
| COCAEIN 43-1395056 | Education | MO | $5,999,290Mid-sized | 83.54 |
| Cocoon HouseEIN 91-1497667 | Human Services | WA | $4,854,869Mid-sized | 87.51 |
| Cold Spring Harbor LaboratoryEIN 11-2013303 | Research and Public Policy | NY | $147,631,524Large | 92.80 |
| Collaborative for Academic, Social, and Emotional LearningEIN 20-5884201 | Education | IL | $6,773,512Mid-sized | 88.56 |
| College Bound, CAEIN 95-4604550 | Education | CA | $709,979Small | 68.46 |
| College Bound, MOEIN 20-4768985 | Education | MO | $2,509,817Small | 91.73 |
| College Golf FellowshipEIN 55-0798282 | Religion | CA | $2,573,949Small | 81.83 |
| College Now Greater ClevelandEIN 34-6580096 | Education | OH | $12,466,427Mid-sized | 95.47 |
| College PossibleEIN 41-1968798 | Education | MN | $16,391,039Large | 91.38 |
| College TrackEIN 94-3279613 | Education | CA | $18,429,592Large | 96.15 |
| CollegeBound FoundationEIN 52-1598921 | Education | MD | $3,336,619Small | 85.81 |
| Collision Repair Education FoundationEIN 36-3768028 | Education | IL | $11,564,561Mid-sized | 92.54 |
| Colon Cancer Coalition EIN 30-0377727 | Health | MN | $1,402,947Small | 86.69 |
| Colonial Heights Food PantryEIN 20-8932952 | Human Services | VA | $1,061,505Small | 77.42 |
| Colonial Williamsburg FoundationEIN 54-0505888 | Arts, Culture, Humanities | VA | $138,893,757Large | 84.28 |
| Colorado Center on Law and PolicyEIN 84-1264154 | Research and Public Policy | CO | $1,154,061Small | 92.33 |
| Colorado Children's CampaignEIN 74-2374672 | Human and Civil Rights | CO | $2,182,396Small | 91.93 |
| Colorado Education InitiativeEIN 26-1597530 | Education | CO | $7,489,959Mid-sized | 85.38 |
| Colorado Neurological InstituteEIN 84-1100975 | Health | CO | $2,596,095Small | 80.93 |
| Colorado Public RadioEIN 74-2324052 | Arts, Culture, Humanities | CO | $17,648,179Large | 95.44 |