  We present the first Event Horizon Telescope (EHT) images of M87, using
observations from April 2017 at 1.3 mm wavelength. These images show a
prominent ring with a diameter of ~40 micro-as, consistent with the size and
shape of the lensed photon orbit encircling the "shadow" of a supermassive
black hole. The ring is persistent across four observing nights and shows
enhanced brightness in the south. To assess the reliability of these results,
we implemented a two-stage imaging procedure. In the first stage, four teams,
each blind to the others' work, produced images of M87 using both an
established method (CLEAN) and a newer technique (regularized maximum
likelihood). This stage allowed us to avoid shared human bias and to assess
common features among independent reconstructions. In the second stage, we
reconstructed synthetic data from a large survey of imaging parameters and then
compared the results with the corresponding ground truth images. This stage
allowed us to select parameters objectively to use when reconstructing images
of M87. Across all tests in both stages, the ring diameter and asymmetry
remained stable, insensitive to the choice of imaging technique. We describe
the EHT imaging procedures, the primary image features in M87, and the
dependence of these features on imaging assumptions.
