The number of known periodic variables has grown rapidly in recent years. Thanks to its large field of view and faint limiting magnitude, the Zwicky Transient Facility (ZTF) offers a unique opportunity to detect variable stars in the northern sky. Here, we exploit ZTF Data Release 2 (DR2) to search for and classify variables down tor ∼ 20.6 mag. We classify 781,602 periodic variables into 11 main types using an improved classification method. Comparison with previously published catalogs shows that 621,702 objects (79.5%) are newly discovered or newly classified, including ∼700 Cepheids, ∼5000 RR Lyrae stars, ∼15,000 δ Scuti variables, ∼350,000 eclipsing binaries,∼100,000 long-period variables, and about 150,000 rotational variables. The typical misclassification rate and period accuracy are on the order of 2% and 99%, respectively. 74% of our variables are located at Galactic latitudes, |b| < 10◦. This large sample of Cepheids, RR Lyrae, δ Scuti stars, and contact (EW-type) eclipsing binaries is helpful to investigate the Galaxy’s disk structure and evolution with an improved completeness, areal coverage, and age resolution. Specifically, the northern warp and the disk’s edge at distances of 15–20 kpc are significantly better covered than previously. Among rotational variables, RS Canum Venaticorum and BY Draconis-type variables can be separated easily. Our knowledge of stellar chromospheric activity would benefit greatly from a statistical analysis of these types of variables. These supplementary materials contain g and r bands single-exposure photometry for 781,602 periodic variables in Table 2 of the paper. SourceID is the internal source identifier joins these attachments to Table 2. Example: For variable star ZTFJ000000.19+320847.2 in Table 2, the SourceID=3 is adopted to search corresponding single-exposure information in both 'ztf2g' and ''ztf2r'. File Description: ztf2g g band single exposure photometry data of variables from ZTF2. SourceID, RAdeg, DEdeg, HJD, gmag, e_gmag, g_flag ztf2r r band single exposure photometry data of variables from ZTF2. SourceID, RAdeg, DEdeg, HJD, rmag, e_rmag, r_flag Table2 ZTF Variables Catalog. Table6 ZTF Suspected Variables Catalog.